same plate, a little below the superposed images of the corona, there is an over-exposed spectrum of the thin crescent of the reappearing sun-which printed itself after the camera had been shifted from its original position, at the moment that I covered the prism with its cap; for at the end of totality I had put an end to the exposure by covering the front of the prism with my hand, and afterwards in removing my hand and placing on the cap this exposure seems to have been made. Although this happened by accident, it turns out to be a very convenient scale of reference. At first it misled me and many of my friends, as we took it to correspond to the spectrum of Young's stratum seen at the east and west limbs. This mistake was rendered possible by the fact that the spectrum is much over-exposed, and the central parts in the neighbourhood of the G line are rendered quite transparent by over-exposure; but the explanation is now clear, and it serves to show that the superposed images of the corona which have imprinted themselves correspond to only about a fourth or a fifth part of the length of the part of the spectrum which can be photographed, and, conse quently, that the combined light of the superposed images at either end of the spectrum was not sufficient to impress itself upon the photographic plate.

A CHARGE AGAINST BRITISH MECHANICS. HE following extract from a letter, written by THE extract, a waisted in America. We expect to hear its authenticity denied, for either Mr. Bell must be an extraordinary inventor, or he went to the wrong places with his work. There is no difficulty whatever in getting anything made provided the cost is not a consideration, and the reflection on the capacity of our mechanics sounds strange from the lips of a man who must know that the majority of the very men who would be employed in the country of his adoption on such work as he mentions, are British, German, and French artisans. Prof. Bell writes: "If you want to know the reason why invertors are more numerous in America than they are here, come and live for six months in England. If you wi-h to know how it feels to be brimful of ideas, and yet to be unable to have one of them executed, come to England. If you wish to know how it feels to have to wait for a month to have the simplest thing made, and then to be charged a man's wages for two months, come to England.

"You will here be unable to see the interior of a workshop or to come into direct contact with your workmen, and the people seem incapable of working excepting in the ruts worn out by their pre: decessors. They are absolutely incapable of calculating any new design without the most laborious oversight from the inventor, and their masters, instead of encouraging invention, do all they can to put a stop to it, by refusing admission to the workshops, and charging the most exorbitant prices for experimental work, avowedly because they don't want such kind of work, it gives more trouble than it is worth,' and if you must have new things made you must expect to pay for them. It is in vain that I say I have no objection to pay if I can only be allowed to oversee my own work. It is in vain that I say I am willing to pay anything to have my work done, and that what I object to is having to pay for not having it done. It is the same everywhere. Not only is your work not done, but you bave to wait so long for the simple-t things, that your ideas cool, and you get quite exasperated at your inability to do any hing."

HOW TO TEST A LATHE.* то test if the cone spindle be parallel with the ways or shears, bore a long hole in a piece of cast iron, using a stout tool-bolder and a short stiff tool, taking a fine cut with a tool having its cutting edge slightly rounded, with a feed of 16 to an inch, at a speed of 25ft. per minute. Let the tool feed through the hole and back again, so that it may be definitely known that the tool does not spring away from the work. Then, without moving the tool from the cut, wind the tool to the entrance of the hole, and let it stand there while the lathe runs forty or fifty revolutions. Traverse the tool to the other end of the hole, and let it stand while the lathe runs again. Then stop the lathe and traverse the tool (without taking it from the cut) along the hole, and if it marks a line stronger at one end of the hole than at the other, the tool has sprung and another fine cut must be taken as before; but if not, and the hole is parallel, the spindle is true. To avoid the wear of the tool it must be made as hard as possible. If the cut was started at the front and the hole bored is smallest at the back, another cut should be taken, commencing at the back and feeding towards the front. If the hole is still smallest at the back, the lathe cone spindle is not parallel with the ways.

* By J. R., in Scientific American.

In taking a cut down a radial face, to test the truth of the cross slide of the rest, the cut should be started from the periphery, for the following reasons:-It is obvious that to some degree (how ever slight it may, under careful manipulation, be) the tool will become dulled as the cut proceeds, Now, with an equal depth of cut, and under equal conditions, there is more strain and wear upon the tool edge when cutting the larger than when cutting the smaller diameter. Suppose, for example, that in the figure we have the radial face, A A, and that the tools, B and c, are each taking off a cut of 1-16in. deep having an equal feed; then from the lines, DE, we may perceive that the metal in the act of being severed by the tool, B, is much better supported by the metal behind it than is the metal being severed by c, and it follows that by beginning the cut at the outer diameter the strain upon it will get less, while the tool edge becomes duller; hence better results will be obtained than if the duty increased as the tool edge dulled.

SCIENTIFIC SOCIETIES.

SOCIETY OF ENGINEERS.

To determine whether the cross slide is at a right angle with the ways or shears, take a fine cut over a radial face, such, for example, as the largest faceplate, and test the finished plate with a straight. edge. If the face-plate runs true and shows true with a straight edge, so that it is unnecessary to Ta meeting of the Society of Engineers, hell take a cut over it, grind a piece of steel a little AT rounding on its end, and fasten it in the tool-post or Spice, president, in the chair, a paper was read by on Monday evening. October 7th, Mr. R. P. clamp, with the rounded end next to the face-plate. Mr. Geo. G. André on "The Application of Electri Let the rounded end be about fin. away from the city to the Ignition of Blasting Charges." The face-plate, and then put the feed motion into gear, Author described the advantages afforded by electriand, with the steel near the periphery of the face-cal firing as of two kinds: (1) Those due to the plate, let the carriage feed up until the rounded steel simultaneous discharge of the blasts, and (2) those end will just grip a piece of thin paper against the resulting from the nature of the means of ignition. face-plate tight enough to cause a slight strain in He showed, by means of a diagram, that the total pulling the paper out, then wind the tool in towards amount of work to be done was considerably the lathe centre and try the friction of the paper diminished by simultaneous discharges, and that, as there; if equal, the cross slide is true. a natural consequence, the saving of time and money that another distinct advantage lay in the fact that was proportionately increased; moreover, he proved the whole face of the rock was brought away comparatively clean and smooth, no projections or bosses being le!t, as in the case of single blasts. The main advantage resulting from the nature of the means of ignition was the increased safety of the operator owing to the fact that the charge could not possibly be ignited until he had had sufficient time to retira to a place of safety. With the ordinary safety fuse, however, it is otherwise, the chargeman, after igniting the fuse, having to retire hastily from the spot, and always incurring a certain amount of risk. The author next explained that the majority of blasting accidents were due to the unexpected ex plosion of shots which had been approached by the men under the conviction that they had missed fire through a defect in the fuse. This difficulty is entirely removed by electrical firing, inasmuch as, in case of failure, the charge cannot possibly be ignited afterwards. Another material advantage lies in the gain of speed, due to the same cause, all delay occasioned by having to wait the prescribed timesome 15 or 20 minutes-before returning to the shot which has missed, being avoided. A minor advantage is the possibility of igniting the charge in the middle, a mode of firing which gives the best results. In proceeding to describe the electric fuse, the author laid down the following five requirements which they must satisfy :-(1) They should be so constructed as to be easy applicable to the charge of explosive used. (2) They should not be capable of being injured by rough handling. (3) They should be so prepared that the operator may have no difficulty in putting them into circuit. (4) They should be certain to explode under ordinary conditions of firing, and (5) they should explode simultaneously in large numbers. Electric fuses are of two kinds: the former may be ignited by the current from a battery, Quantity" fuse, and the "Tension fuse; the and the latter by that from a frictional, or other machine of high tension. In describing these two varieties, Mr. André stated that the tension fuse was most satisfactory, as the mode of firing was more easy and secure with the machine than with the battery; and further that, with a higher tension, a larger number of shots might be fired simultaneously; He next described the tension fuses now in use, all of which, he stated, fulfilled the first four requirements, but broke down in the fifth. This difficulty the author has partially overcome with a fuse of his own construction. Upwards of 20,000 of these fuses were fired in groups of from 10 to 16, under all possible conditions, without a single miss-fire. The paper concluded with a few remarks upon the condi tion of the frictional machine at the time of using.

E

ப.

To test the workmanship of the back head or tailstock, place the forefinger on the spindle close to the hub whence it emerges, and observe how much the hand wheel can be moved without moving the spindle; this will show how much, if any, lost motion there is between the screw and the nut in the spindle. Next wind the back spindle as far as it will go, take hold of the dead centre and pull it back and forth, when an imperfect fit between the spindle and the hole in which it slides will be shown by the lateral motion of the dead centre. Wind the dead centre in again, and tighten and loosen the spindle clamp, and see if doing so moves the spindle in the socket. Wind the dead centre out again and slide the tailstock up the lathe bed until the dead centre nearly touches the live one, and after bolting the tailstock to the lathe bed, bring the centrepoints close together and see if they coincide. If the tailstock sets over for turning tapers, the setting screws may be operated to adjust the centres.

In any event, the lathe centres should be of equal

height, or the lathe will not turn true. It is as well
to turn the back centre partly in its socket while
making this test, so as not to be deceived by any
want of truth in the back or dead centre.

To examine the slide-rest, move the screw handles
back and forth to find how much they may be moved
without giving motion to the slides; this will deter-
mine the amount of lost motion between the collars
the nuts in which they operate. To try the fit of
of the screws and between the screws themselves and
the movable slides in the stationary sliding ways or
Ve, remove the screws and move the slide so that
then move the slide back and forth laterally to see
only about one half inch is in contact with the Vs,
if there is any play. Move the slide to the other end
glide to take up any play at either end. Then clean
of the Vs, and make a similar test, adjusting the
the bearing surfaces and move the slide back and
forth on the Vs, and the marks will show the fit,
while the power required to move the slide will show
the parallelism of the Vs.

If the lathe carriage have a rack feed, operate it slowly by hand, to ascertain if it can be fed slowly and regularly by hand, which is of great importance. Then put the automatic feed in gear, and operate the feed gear back and forth, to determine how much it can be moved without moving the slide rest. To test the fit of the feed screw to the feed nut, put the latter. He has been assumed in this method of the latter in gear and operate the rack motion back antifor that means of adjustment pre provided whereby any play in the cone spindle bearings may

be taken up.

Thomson's Steam Lifeboat.-A number of gentlemen recently paid a visit to Messrs. Walker's yard, Deptford, to inspect the frame of the Duo in Uno, a steam lifeboat which is being built on the principles laid down by Mr. Edward Thompson in a paper read by him at the last meeting of the Institute boat is built are as follows:-That a vessel built with of Naval Architects. The principles on which this a cellular frame, and tunnelled after body with a single bow, will be practically unsinkable; that the free from "racing," out of reach of injury from propeller, when placed between the bodies, will be wreckage, and that to a great extent the loss of that the position of the screw working near the power from the slip of the screw will be obviated; centre of the vessel, in solid water, will enable her to be reversed within her own length, at the same time retaining her steering powers unimpaired; that the issuant water from the tunnel being left in a straight course bebind will not hurt the banks of a river or canal, and will thus be invaluable for inland navigation; that the vessel will be able to carry a much greater spread of canvas, while the screw (placed as proposed), when disconnected, will be no impediment to sailing; and that boats of this description would be extremely useful in a heavy surf, boat is 32ft. in length by Sit. in breadth, having a and as Channel or ferry steamers. The experimental mean draft of 2ft. 6in., and will be ready about tall end of the present month, wher, a trial trip will probably be made with her.

SCIENTIFIC NEWS.

Entomologist gives a list, and we have no doubt
that specimens to replace those damaged will
soon be forthcoming, as it is recognised as a
type collection. Mr. Doubleday's systematic
lists form a classification commonly used, and
it is evident that Bethnal-green is not so far
away but that a goodly number of students can
find their way to it. We doubt if so many
applications would have been received at South
Kensington.

THE
HE scientific news of the week is mainly
electrical, the new light having been
introduced for the first time into show-rooms.
At a shop in Regent-street we have an ordinary
regulator with Siemens' machine, worked by a
gas-engine, and at Messrs. Wells and Co.'s, in
Shoreditch, we have the Jablochkoff candle,
showing off the colours of the marble mantel-
Mr. F. W. Webb is still trying to perfect the
pieces as clearly and almost as brightly as they chain brake. His latest improvements consist
can be seen by daylight. There a Gramme
of an arrangement of small and large cylinders,
machine, capable of distributing the current to with corresponding pistons operated by air or
six lights, is at work, the generator and the dis-other elastic fluid in such a manner that the
tributor being driven by separate belts, and
requiring, we imagine, from eye estimation, pressure must be constant to keep the brake
blocks off the wheels. The brakes are actuated
rather more horse-power than is usually sup by chains and friction drums, brought in and
posed to be necessary. The power of the light out of contact with the axles. A friction drum
is said to be "100 gas lights," but one naked is applied to each vehicle, and a "rope" is ex-
Jablochkoff candle can be regarded with ease tended between the engine and tender and van
at a distance of two yards, and the eye can be of each train, to keep the friction drums out of
steadily kept upon six without any great incon- contact with the axles. The brakes are applied
by allowing the rope to slack.

venience. We should like to have some accurate photometric tests of the illuminating power, and some rigidly-conducted dynamometer trials of the force employed to drive the machines. The light of six naked candles is very fine, because it is scattered in all directions, but the arc in one naked candle looks very much like a mere point of brilliant light, which, however, in a large opaline globe, makes a splendid lamp. Even if as powerful the yellow light of gas would put it in the second place wherever the best means of illumination is concerned. A Jablochkoff candle lasts about an hour and a half, but as four are arranged in each lamp, and an ingenious automatic arrangement operates a switch, and turns the current to a fresh candle as one is burnt out, the light is practically continuous for six hours.

The Woolhope Club's fungus foray was duly held as announced, and appears to have been fairly successful. Owing to the scarcity of fungi of the edible kinds Dr. Bull had to confine himself to preparations of Hygrophorus pratensis and Agaricus nebularis, but sufficient fungus soup was forthcoming to make over fifty diners gastronomically satisfied. A goodly number of rarities were found during the forays. The Cryptogamic Society of Scotland commenced its annual conference on Oct. 9, and the next day had received so many different specimens from all parts of the country that it was necessary to clear out another building for their proper display. On the first foray in Penicuick woods about 500 specimens were found, one-a Polyporus giganticus-30 large that two men were required to carry it to the station. Mr. Potts, of Lasswade, in the course of his remarks, stated that carbolic acid was the best cure or preventive for dry rot.

Prof. Nordenskjöld has sent news of his expedition to Stockholm. It left North Cape about the end of July, and reached the Yenisei on August 6. He proposed to start on August 10. He reports the Kara Sea free from ice, with the exception of a little scattered drift near White Island.

M. Mouchez having submitted a project for the formation of a collection of objects relating to the history of astronomy, and of the Paris Observatory since its foundation, has obtained the sanction of the Minister of Public Instrucinstruments, drawings, and models, the collection will include portraits of those who have made the observatory renowned either by their works or their discoveries.

tion. Besides

A simple instrument has been devised for ascertaining the presence of gas in coal-mines. The invention is based on the marked difference in the glow of red-hot platinum in air free from or contaminated by marsh-gas. It is said that it will detect the gas when in the proportion of 1 in 60, and it should, therefore, be of some use in preventing colliery explosions. Here is a note for those who opposed the Bethnal-green Exhibition. The late Mr. Doubleday's collection of Lepidoptera is located there, the British species occupying 106 drawers, for which a catalogue was prepared by the late Mr. Andrew Murray. Last year there were no fewer than 1,492 applications for permission to examine the collection, but unfortunately 238 species have been destroyed by mites. The

A trial of 33in. and 42in. railway wheels having been made upon long-distance express trains, the Boston and Albany Company have determined to use the larger wheels for the New York through passenger traffic. The ordinary 33in. cast-iron wheel lasts about four years, but latterly the steel-tired wheels have been tested and found to yield better results; consequently the new wheels will have steel tires. Cast-iron wheels were great favourites at one time in America.

Mr. Edison has set the fashion, and we shall soon have all sorts of announcements as to the electric light. We expect to hear soon that it can be had in some way from odic force or etheric force (see p. 374, Vol. XXII), and cost nothing at all. The latest "note," is in the Dundee Advertiser:-"We were informed yesterday by a gentleman from London that an ingenious mechanic has discovered a simple method of generating the electric current without the machine power required for the Gramme, Siemens, and other methods, and by his system, after an outlay of about £20, a house can be lighted by electricity at the cost of only a few pence per month. This invention has met the approval of an influential engineer, who is supplying the means for perfecting it, and it is expected that before long it will be brought before the public."

According to the latest news Mr. Wallace's new dynamo-electric machine reproduces as current 80 per cent. of the power employed to drive it.

With regard to the progress of drunkenness in Germany the Correspondance Economique notes the fact that in Osnabrück the consumption of brandy, which in 1872 was 287,000 litres (in round figures), rose in 1873 to 343,000 litres, in 1874 to 384,000 litres, in 1875 to 474,000 litres, and in 1876 to 481,000 litres, or 16 litres on an average per head of the population.

Cases of the bursting into fragments of toughened glass have, it is known, been repeatedly recorded of late. One such case is now reported from France. An evaporating dish of De la Bastie's toughened glass had been in use one month in the stearine factory of M. Fournier. It burst into pieces one day, when, after being slowly heated to 110° C., and then cooled, it was placed on a perfectly clean weighing scale, and the chemist using it escaped severe injury only through the caution with which he had handled the scale.

In a recent number of the Bulletin de la

Société d'Encouragement is an interesting re-
port on M. Gilbert's pencil manufactory at
Givet, in the Ardennes. The superiority of
the products from these works is said to be due
(1) to exclusive use of the best graphite of
Bohemia, which is about as rich in carbon as
the graphites of Cumberland and Siberia, and
is much better adapted for manufacture of
artificial crayons; (2), to the minute care
with which it is washed and freed from all
foreign matters; (3), to the prolonged work-
ing up and grinding it undergoes, with clay, in
The crayon
mills of special construction.
paste, worked and withdrawn by means of
mechanical presses, passes into furnaces hav-
ing a high temperature, and is submitted to
incessant surveillance. M. Gilbert's establish-
ment consumes annually nearly two hundred
thousand kilogrammes of Florida cedar wood,
besides a considerable quantity of lime tree
and other white woods. His pencils are stated
to have a beautiful black, superior to the
metallic grey of English crayons, and to be
capable of employment on all smooth papers
on which many pencils do not bite. Also, as
the gum used in their composition is very
dilute, it is possible with only one crayon to
obtain nearly the same effects as with various
numbers. The pencils are sold very cheaply,
e.g., pencils of white wood at 1fr. 40c. the
gross. It is added that M. Gilbert treats his
work people in a very exemplary way, providing
medical attendance for them, and continuing
their wages through illness, &c.

In a thesis recently presented to the Faculty of Medicine in Paris, Dr. Magnin gives a résumé of our present knowledge of bacteria, to the following effect: 1. Bacteria are cellular Mr. C. Tomlinson, F.R.S., referring to the organisms of vegetable nature. 2. Their or. article on page 86, "The Electrical Tourni-ganisation is more complicated than was long quet," forwards a copy of a paper published in supposed; the chief points demonstrated being the Philosophical Magazine for 1864, from which their structure, the presence of hairs, the it is clear that the experiments detailed by Mr. nature of the substances contained in the Tomlinson cover ground more extensive than protoplasm. 3. The forms of torula, zoophaa, that occupied by those of M. Bichat. We may leptothrix, mycoderm, &c., whose signification publish an abstract of the paper in an early is best known, correspond to different states of number. the same species. 4. The manifold affinities of bacteria, on the one hand, with alge on the other, with fungi (variously regarded by authors), and their development, unknown for the majority of the species, make any classifi cation at present only provisional. development, well established, of several species of bacillus proves that the multiplication of bacteria may take place, not only by scissiparity, but also by the formation of spores, and even by veritable sporanges. 6. These spores or permanent germs are the prin cipal means of dissemination of these low organisms. 7. Their role in fermentation, putrefaction, contagious diseases, and surgical lesions, notwithstanding the considerable number of works on the subject, cannot yet be defined with certainty.

Among the resolutions adopted by the recent International Congress for Study of Questions Relating to Alcoholism were two to the following effect:-Considering it is now proved, by experimental research and by statistics, that while the abuse of brandies of any kind may cause toxical phenomena, the presence in these brandies of alcohols other than ethylic notably augments their hurtful action; considering, further, that the study of these questions to be profound needs to be prosecuted a certain number of years, the Congress unanimously thought it advisable (1) that governments should be invited, not merely to prevent and repress the abuse of alcoholic drinks by legislative measures, but to make every effort in their power to secure that brandy destined for consumption be purified and rectified as much as possible; and (2) that a permanent international commission be appointed to collect all the facts relative to study of alcoholism, to study the means of conbatting it, and to promote the holding of further congresses for continuing the work of the congress of Paris. After nominating the members of a commission it was decided that the next congress should be held in 1880 at Brussels or Stockholm.

5. The

For

Some excellent results in utilisation of solar heat have been obtained lately in Paris by M. Mouchot, with a large reflector, boiler, and accessories according to his system. example, on the 22nd September, with a continuous sun, but slightly veiled, a pressure of 62 atm. was obtained, and with a constant pressure of 3 atm. a Tangye pump was made to raise 1,500 to 1,800 litres of water hourly 2 metres. (Farther details will be found in Comptes Rendus, 30th Sept.)

[We do not hold ourselves responsible for the opinions of
our correspondents. The Editor respectfully requests that all
sommunications should be drawn up as briefly as possible.]
ENGLISH MECHANIC, 31, Tavistock-street, Covent-garden,
All communications should be addressed to the Editor of the
W.C.

All Cheques and Post-office Orders to be made Payable to
J. PASSMORE EDWARDS.

which appears.

Apropos of some recent researches in dimen- LETTERS TO THE EDITOR. sions of cranium a writer in the Bibliotheque Universelle remarks on the substantial similarity of the human mind everywhere, and the differences between races more or less advanced being merely of degree. He cites in illustration a passage from an old Chinese philosopher named Li, recently translated. This tells of one Yin, a man of high birth and great wealth, who worked his servants very hard. One old servant was sorely tried thus, and at night he ** In order to facilitate reference, Correspondents, when went to sleep completely exhausted. But speaking of any Letter previously inserted, will oblige by every night he dreamed he was a sovereigntioning the number of the Letter, as well as the page on prince; he walked about in a sumptuous palace, and had all he desired. When compassionated about his lot he dwelt on this fact as a reason for contentment. The master, on the other hand, toiled all day in search of pleasure and increase of fortune, but at night, in his dreams, became a miserable slave. Thus the one was happy by night, the other by day. Now, Pascal, who could not have seen Li's writings, has a passage to the same effect. If we dreamt the same thing every night, he says, it would perhaps affect us as much as the objects we see every day. And if an artisan were sure of dreaming every night for twelve hours that he was a king, I believe he would be almost as happy as a king who should dream twelve hours every night that he was an

artisan.

The celebrated Encke was obliged to accept the hypothesis of a resistant medium in celestial space to explain the mean acceleration of motion of the comet which bears his name. The exactness of Encke's calculations having been doubted, M. Asten, astronomer at Pulkova, has recently made a new determination of the comet's orbit, and the result is confirmatory. The mean acceleration of the comet is reckoned by M. Asten at + 0"-1044184 ± 0·0001353. This acceleration is produced chiefly in the part of the orbit contiguous to the perihelion, as if the density of the resistant medium were greatest next the sun. In regard to this communication (to the St. Petersburg Physical Society) M. Mendeleef remarked that the perturbations of motion of Encke's comet may be more probably explained by the action of extremely rarefied exterior layers of the solar atmosphere, which, nevertheless, is limited, for the gases appear to have a limit of rarefaction. This explains also the fact that Faye's comet, which does not pass so near the sun, does not experience acceleration, its movement taking place in the space deprived of gas.

New Horseshoe.-A new form of horseshoe, which may be fastened to the hoof without the use of nails, has been designed by Dr. J. Hirsiger, and is now being tested at the Horse Guards and elsewhere. Any efficient means of fastening the shoe without nails is a great acquisition. Hirsiger's shoe is of the common form, but without side and front ears, and instead of nail holes is provided with screw or rivet holes, by which it is attached to a jointed plate of shoe form, and provided with thin side and front ears very much like those of a common shoe. These ears stand inwards, so as to fit the hoop, and one of the ears being upon the jointed part of the plate shoe, the latter, with the actual shoe fastened on, can be slipped on to the hoof. The jointed part of the thin shoe is then held in position by means of one set screw passed into the rear of the actual shoe.

Invention for Extinguishing Fire.-A private trial was made last Thursday week, at Hendon, of Messrs. Atkins, Allen, and Aston's invention for extinguishing fire. The apparatus consists of a small drum-shaped stove, about 20in. high and 14in. in diameter, charged with a mixture of animal and vegetable charcoal and coke. This stove was connected by a lin. pipe with the inlet supply pipe of a fire-engine. Instead of the exhaust of the pump drawing in water alone it sucks in simultaneously water and the gases given off by the burning charcoal and coke, the action being somewhat similar to placing two straws in one's mouth, sucking in water through the one and air through the other, and then violently puffing out the combined air and water through another pipe. It is claimed for the invention that the gases generated in the stove, although presumably largely composed of carbonic acid gas, in place of being a deadly compound may be inbaled with no more adverse effect than is experienced when breathing in an atmosphere of ordinary steam. The experiments, says the Engineer, were con idered to prove the invention of considerable value.

"I would have everyone write what he knows, and as anch as he knows, but no more; and that not in this only, but in all other subjects: For such a person may have some particular knowledge and experience of the nature of such a person or such a fountain, that as to other things, knows no more than what everybody does, and yet, to keep a clutter with this little pittance of his, will undertake to write the whole body of physicks: a vice from whence great inconveniences derive their original." -Montaigne's Essays.

PARIS AND THE EXPOSITION.

when clad in linen.

and showing the remains within. Here are gigantic
and fearful images of stone which have long outlived
the names of those who wrought them, and have even
survived the history of their origin Here are flint
celts, arrow tips, hammers and the like by thousands;
corroded weapons, corroded instruments, fragments
photographs of rifled tombs and caves; instruments
of pot, weapons of bronze and iron, drawings and
and ornaments of gold-femoral bones-teeth of
men, of bears, and various animals-jawbones of all
sorts, and bones of divers kinds of reptiles-jugs of
the crudest kind, some whole, some broken, and
some carefully repaired-a stupendous set of leg
bones-human, as far as I can tell, but some 5ft. or
so in length; models of human subjects of all
nations, clothed in their proper garb-models of
human brains, human faces (mostly ngly), and
models of human eyes; restorations and models of
ancient caves-cave towns, castles, forts, and ram-
parts; a model of Stonehenge, and masses of cave
deposits, in which human bones and various sorts of
débris may be seen. Here is a group of mummies
in sitting postures; here is another group of similar
unearthed remains-two looking intensely miserable.
and one extremely cute. Here is the mummy of a
South Sea Islander (for sale), full length, stripped of
models of feet, normal and distorted-pictures and
everything, and wonderfully preserved. Here are
photographs of people who are blind-bones found
in the trunks of trees, and the trunks in which the
bones were found. Here, in short, is a world of
material for the study of our kind-some of it
beautiful, some of it saddening, some of it horrible,
much of it repulsive, but all of it eminently instruc-
tive.
D. Winstanley.

CARL ZEISS'S NEW OIL-IMMERSION
OBJECTIVE OF-1-12in. FOCUS-NO. 5.
[14971.]-IN No. 683 (letter 14253) of the
ENGLISH MECHANIC I reviewed a new oil-immer-
sion objective of in. focus, and I expressed then the
hope that Professor Abbe and Mr. Zeiss might soon
the oil immersion principle. This hope has recently
succeed in constructing higher powers than the on
been realised by the production of a 1-12th, of which
I received a specimen some weeks ago, and of which
a short notice may be of interest to microscopists.

here by noticing the variations in the sensibility of
[14970.]-I HAVE been much surprised since coming
the human body to the feeling of heat. I brought
with me a few suits of linen drills," which I had
procured some time before when intending to go
elsewhere. On the chimney-piece of my chambre à
coucher I have a self-registering maximum and
minimum thermometer (a good instrument). I came
to Paris in March, when the weather was decidedly
cold. As the temperature gradually increased I
noticed that my ordinary clothing became uncom-
fortably hot if my thermometer indicated 70° Fabr.
when I rose at 8 o'clock; and accordingly when that
temperature was indicated on getting up I made it
my rule to adopt the linen, and felt at a convenient
temperature throughout the day. As summer
advanced, and the heat increased, I never felt hot
had risen to 97° F. in the shade, on the heights of
Even when the thermometer
St. Cloud I felt no uncomfortable sensation of being
hot, and furnished with an Indian cape-cap strolled
leisurely in the blazing sun for hours, the ther-
mometer indicating 125° F., without feeling uncom
fortably hot, and without being conscious of
perspiration. In England I have been driven to
desperation when my thermometer showed only 82
F. in the shade, being clad in the usual English garb.
I am told by men whose travelling experiences are
far greater than my own that they have never been
anywhere where the heat of summer is more hard to
bear than it is in England, and for the simple reason
that having but little heat we are prepared for none.
During the hot weather here I lived almost wholly
upon vegetables and fruits-peas, beans, huge slices
of melon and the like-no meat, and above all no
abominable fat. To this circumstance, and to the
linen clothes I wore, I attribute my immunity from
the sensation of being hot during the summer
weather. I have strolled into the square of St. Cloud,
linen clad and "cool as a cucumber," when five or
six hundred of my compatriots have been trundled
in by Cook and Gaze, their faces fiery red, the
perspiration running from them in a stream, and
they meanwhile puffing and blowing like so many
locomotives. The windows seemingly of all French
houses are also adapted for warm weather. Instead
of our miserable idea of a horizontal section, which
permits at most only one-half the window aperture
to be opened for the admission of the air, the French
employ the vertical division, and open the windows
inwardly on hinges as we open doors. The window aper-
tures are also large, or rather high, the width being
much the same as with ourselves. In the room where
sit, for instance, there are two windows. They
descend to within 18in. of the floor, and ascend to
within 4in. of the ceiling, the glazed portion being
about 8ft. high. Outside there are latticed shutters.
When the windows are open and the shutters closed
the sun is effectually kept out, and the free circulation
of the air is scarcely interfered with. A light
balustrade of iron, within the shutters and without
the glass, serves to prevent falling through the
windows. And this style of window seems absolutely
universal here in conjunction with dwelling-houses.
Why retain the wretched things we have in England,
with the Venetian shutters inside instead of out?
Thus placed they may keep the sun's rays from
falling on the inmates, but they do not exclude the
heat, and the glass beyond merely causes its accu-
mulation, making your sitting rooms like a set of
stoves. Speaking of temperatures which the human
frame can bear brings me by a natural process to the
Annexe Anthropologicale du Trocadèro. He who
indulges in "the proper study for mankind" will
here find an abundance of material for his reflections.
There is a display of, I should think, some thousands
of human skulls, heads, casts, and preparations. Nearly all that I stated in letter 14253 about the
Here are evidences of pre-historic man-models of th is applicable to the new 1-12th, and I beg to
ancient tombs, with skeletons strewn "pell-mell" refer both to that letter and to abler articles on the
models of ancient tombs, with skeletons in single new th oil immersion lenses which have appeared in
blessedness and solemn form-models of ancient the Journal of the Royal Microscopical Society:
tumuli before being cut, and models of them open,
It is to be regretted that Professor Abbe and Mr.

This new object-glass is similar in external appearance to the th referred to, the optical combina tion being contained in a brass setting barely fin long, which is screwed to an adapter provided with the universal screw, and which gives to the whole the appearance of an English objective. The front lens has a diameter of about 1-12th inch, and is set in a white metal front. The workmanship is in every respect of the best kind. This 1-12th has, like its predecessor, the th, no screw collar, as ite front lens has to be immersed in a small drop of cedarwood oil, whose refractive power is practically equal to that of crown glass, of which both front lens and the covering glass of the object consist Any small correction necessary has to be made by means of the draw-tube. For observations by central light a more dispersive fluid is required in order to secure an image free from chromatic aberration, and such a fluid can be obtained by mixing together fennel-seed oil and clear olive oil in a proportion which can be readily ascertained by means of a bottle having two ground parallel sides and a crownglass prism cemented to its stopper, which Mr. Zeiss supplies along with his oil-immersion lenses. I find the magnification of this new 1-12th with Ross's A eyepiece, at a distance of 10in. from the latter to be fully 580 diameters, and the working dis tance about 1-13th inch. The angular aperture is stated to be the same as that of the th-viz., equal to a balsam angle of 113°, and considered, according to its "numerical value," larger in the proportion of 1.25 to 1, or of 5 to 4, than that of a dry objective of 180° air angle. To insure the greatest possible resolving power of these oil lenses it is necessary that the objects should be mounted in balsam or is any other medium having a refractive index of, at least, 125; or, if mounted dry, that they should adhere closely to the cover.

I am happy to be able to state that I find the optical qualities of this new lens in every respect equal to that of the 4th previously described. The field is perfectly flat and the brilliancy and definition leave nothing to be desired, whilst the resolving power is extraordinary. All the finer diatomaceous tests, such as amphipleura, pellucida, &c., are resolved with the greatest ease and with the atmost distinctness; and, although I have hitherto failed to see, both with the ith and the 1-12th oil-immersion lenses, more than with Powell and Lealand's excellent new formula or some other first-class water immersion lenses, yet I see everything better and easier than with the latter. For the resolution of the markings on diatoms no better lenses could be desired than these Zeiss's oil-immersion lenses.

THE MATHEMATICAL PRINCIPLE OF tion we may affirm to be the harmonic chord Me, se,
THE MUSICAL SCALE.

I trust now that readers of the ENGLISH MECHANIC will no longer be satisfied with the socalled harmonic theory of the text-books. It is an illusion which must eventually lose its seeming solidity and perfection.

their voluntary true minor chord, D grave, F, A, in the hub of the driving wheel. A narrow flange
the key of C, and not the forced false one, D, F, A, of projects from the hub on the inside of the fork; a
the justly-intoned harmonium, and of the harmonic leather strap, cut the proper way of the grain,
theorists. The six chords now obtained complete having one end fixed to the fork, passes round the
the simple form of notes called the major diatonic flange. A small bell chain, also fastened to the fork,
scale, and it is consequently made clear that sim- passes round the strap, extending up the inner side
plicity of ratio is the law of the form of the diatonic of the fork, and is attached to a tube which revolves
scale, and not only of it, but of the entire system of on the steering bar, which tube is actuated by a
the related notes of music, of which this diatonic thumb-piece in close proximity to the handle, so that
scale is, in fact, simply the initiatory portion. The when the thumb-piece is pressed the; chain is
first step beyond the limit of this scale in one direc- tightened upon the leather strap, and a perfectly
uniform power is brought to bear on the driving.
te (in the key of C,-E, G, B), the dominant chord wheel. By this brake the machine may be gradually
which develops the so-called relative minor ascend- brought to a stand upon any declivity without the
ing series. Another chord, related in an equal slightest risk of tipping forward. Of course, this
degree to the diatonic scale, is the bypharmonic brake can be double, but this would only be necessary
chord of doh, the correlative of the me chord-viz., for very hilly country. The single brake may be
doh la, fah; e.g., C, A flat, F.
used with impunity, bat in applying the double
brake caution should be used, as it is extremely
powerful, and the rider should lean well back. All
bicyclists admit that properly constructed roller
bearings are an important adjunct to the bicycle,
but hitherto there has been (with one or two excep-
tions) this considerable drawback-that the rollers
do not always revolve parallel with the spindle, in
which case they are detrimental rather than being a
valuable adjunct. This difficulty has been overcome
by Harrington's Arab roller bearings. Unquestion-
ably every bicycle should be furnished with some
effective means of giving warning of its approach.
Many riders use the small bronze castings, the
perpetual jingling of which are a nuisance to himself
and others who may be with him. Some few carry
a horn, which, in the hands of the captain of a club, or
his attendant, is quite appropriate, but when used
by an ordinary rider it gives him much the appear-
ance of a post-boy or a cad on the loose.
Arab' has its own gong attached, which may be
rung at pleasure by a small thumb-key. Going at
the rate of 8 miles per hour the bell will ring 1,500
times. There is a small indiarubber roller goes down
between the wheel and fork, and as it goes along
every spoke touches the roller and rings the gong.
The gong is fixed in front of the machine, just below
the handles, and measures about 7 or 8in. It is
electro-plated, and has a very effective appearance.
The machine is closely built, and has brass nipples
and lock nuts; the backbone is steel." The price is
rather stiff.
Telescope Tele.

[14972. MR. A. COATES, who (in letter 14908) criticises my treatment of the musical scale in a very acceptable manner, appears, nevertheless, to have not yet perfectly apprehended the principle I advance-namely, mathematical simplicity as the sole fundamental law of the structure of the scale, and of the entire system of the relations of the notes of music as comprehended under the terms chromatic scale, changes of key, &c., all of which are determined by the continuation of the same process Furthermore, I think there is supplied by the or mode of evolution as that by which the simple scale is determined, and not by the accident of what recognition of this simple law of relations of the are called natural harmonics or overtones, and sub-notes of music, an indication that all the relations of tones, none of which belong to music, or coincide the several orders of the phenomena of nature or the with its tones, unless their ratios have their origins universe have in a similar manner their origins in in the primes 1, 2, 3, 5. In my own use of the unities, from which they diverge by immediate words harmonic and hypharmonic, I refer to the degrees, or in other words in unbroken simplest acoustical fitness of notes placed together, either sequences. It may, however, be noted there exist limits seemingly arbitrary, beyond which these melodically or harmonically, the cause of which divergences do not proceed. For instance, as we now acoustical fitness, which we call the being in tune. familiarly know, musical ratios are limited to those we know is owing to the specific simplicity of their mathematical relations, which relations necessarily producible from the primes, 1, 2, 3, 5, and their mulconsist of two reciprocal, and therefore equal orders, tiples. So, likewise, as it is as well to know, the one of which creates the primordial form called the ratios of quantivalence in chemical atomic affinity are restricted within the same primes. In either of harmonic concord, or, in its contracted shape, the major chord; and the other the primordial form these cases there is no known cause or reason why called the hypharmonic concord, or, in its contracted shape, the minor chord.

That there really exists in the structure of the diatonic scale the maximum of mathematical simplicity, allow me again to show by a method which

I think must be clear to every reader.

We begin, then, with the character of a simple note, the first element of music. A simple note consists of a succession, more or less rapid, of periodic vibrations. It is obvious that the maximum of simplicity dwells in this character.

such is the fact.

Hoping, then, I have made made clear this law of
simplicity of the mathematical relations, I will, with
the Editor's permission, in a future letter, attempt
something on the musical relations of the notes

known to some sol-faists as their mental effects.
Oct. 5.
Fred. J. Jackson.

SOUNDBOARD OF THE VIOLIN AND OTHER INSTRUMENTS. Next there are two descriptions of connec [14973.]-SOME time ago I read an account of a tions of notes, each producing what is called a series of lectures on sound delivered by Professor concord. The mathematical ratios of the several Tyndall at the Royal Institution. Treating on the notes of one of them, the harmonic or major con- properties of musical strings he explained that the cord, consist of the numbers 1, 2, 3, 4, 5, 6-e g., sonerous waves produced when the string of a the concord of C, which is C2, C1, G, C, E, G, the sonometer was plucked were not due to the feeble three higher notes of which form its major chord. sounds produced by the string only, but to their The ratios of the several notes the other, the hyp communication through the bridge to the box and harmonic or minor concord, are the reciprocals of the air within it, which thus becomes the chief soundthe former ratios-viz., 1, 1, 3, 4, }, &; e.g., the hyping body. Hence, when strings are employed as harmonic concord of E, which is E, E, A, E, C, A sources of musical sounds they must be associated the three lower notes of which constitute the chord with surfaces which take up (the italics are my designated the minor chord of A. In this second own) their vibration and communicate them to the step, the evolution of the two concords, we still find surrounding air. So far Tyndall. the principle of the maximum of simplicity evidently maintained.

a

The next step after the evolution of the two concords is their coalition into one system. This also takes place in the simplest possible manner, for beginning with the harmonic concord the addition of single note with replicates supplies the hypharmonic concord. Let us illustrate the fact with chordsthat is, omitting the replicates existing in the concords; thus, to the major chord of C, add the note A, and we have A, C, E, G, in which there exist both a major and a minor chord, which is to be regarded as equivalent to the conjunction of the two concords; and in this conjunction, which constitutes the first step in this process of scale formation, we again find that the principle of maximum of simplicity obtains. But this process is susceptible of being continued for the further evolution of concords. It is on the same principle of maximum of simplicity that to the notes, E, G, we may supply the single note, B, and so produce the chord, E, G, B, and then to G and D, the note, B, producing the one chord, G, B, D1. It is needless almost to say that the finding of a chord infers always that of its proper concord.

The

"H. W. W." (query 34137, p. 79) is mistaken in saying the Princess Alice is 11ft. Gin. wide. She is 20ft. 2in. wide.

Both the ideas "A. E. S." (letter 14868, p. 41) speaks of are good-the first one especially, because in the second one the " cover would be about as

liable to be injured as the "iron pot." But the question is not can an unsinkable steamer be built, but can it be built as cheaply? And if the obtaining the buoyancy under all circumstances involve an extra outlay, unsinkable steamers will not be built. Perhaps it would be as well to point out to "Cornishman" (letter 14838, page 18) that the "singular property of figures" is simply that if any of the nine numerals is subtracted from ten, and the remainder added to the numeral first used, the

answer is ten.

Ever since reading these remarks I have been entirely puzzled to understand the modus operandi of this synchronal theory when extended beyond the monochord, as for instance the violin or piano, where two or more strings are vibrated simul taneously upon one soundboard common to all. In such cases does each string vibrate its own particular part of the soundboard, or does each_vibrate the soundboard in its entirety or how? By the first theory we would naturally expect a perceptible diminution in the sound of each note, since their rates of vibration are different, which must necessarily counteract each other's power to move the soundboard. If I play two simultaneous notes on the violin their sound appears to ne equally rein: forced as when played separately. Keep your moind aisy, "Fiddler;" those couplets of cannibalistic ten-C. G." does not know that his question about the dencies are not included in this category. Then nine numerals is one of permutations, or he would with regard to the second theory, I fear it savours 66 not expend an enormous amount of labour" on it. too much of a fellah" running and walking at one and the same time, to stand investigation. This The answer is, I think, 623,420. The horse-shoe mountain of difficulties I have met with may be but problem may be solved by the help of logarithms, a molehill after all, seeing I am one of those recollecting that the number of farthings is 223. Ram Chand Biswas. scientific fellahs who doesn't know nothin'." What say ye, Messrs. Schucht, Fiddler, and Co. on the matter? Non Omnia.

un

On the other hand, the notes, A, C, in the system
so far developed point to the addition of the note,
F, as the next simplest acquirement, which produces
the chord, F, A, C, and, lastly, the notes, F, A, now
THE ARAB BICYCLE.
obtained in like manner, indicate the inception of [14974.]-I TAKE the following from a little book
the grave D,which produces the chord, D grave, F, A, published by the maker of the "Arab" bicycle,
the everlasting odium, I may observe, of the har hoping that it may be interesting to most of the
monic theorists, respecting which Dr. Helmholtz, the readers of this paper. He says:-" The Arab'
great exponent of that theory, remarks:-"Haupt- averages in weight from 331b. to 45lb., according
mann doubts whether in practice the false minor to size-a 48in. strong roadster weighing 331b., a
chord of the key of C major can be distinguished 60in. about 45lb. The spokes of the Arab' wheels
from the minor chord of D. I find that this is most are made of the strongest and toughest known wire,
distinctly and undoubtedly effected on my justly-such as has not been used for the purpose before; it
intoned harmonium, but allow that we cannot expect is especially drawn and plated, to prevent rust.
the correct intonation from singers. They will in- The spoke is only one sixteenth of an inch thick,
voluntarily pass into the minor chord," &c. (page and is brought to tension by a patented arrangement
527, "Sensations of Tone," Ellis's translation) which prevents the torsion of the wire. A spoke
So be it, Dr. Helmholtz, but give me the incorrect can also be applied at any time to the felloe without
intonation, forsooth, of the singers-that is to say, disturbing the rubber tire. The brake power is on

"C. G." (letter 14939, page 98) seems, like "Cornishman," inclined to make some simple arithmetical problem appear wonderful, but how he makes 31 x 2 x 3-that is,

= 6-I don't understand.

THE MICROTASIMETER, [14976. -SINCE writing on this subject (14819, Sept. 13) I find that I have considerably understated the sensitiveness of this instrument. By rendering my galvanometer needles more astatic, and regulat ing the pressure better, I have now no diffienlty in deflecting the needle strongly when my hand is held a foot off, and have repeatedly succeeded at 18in. and even 2ft. off. This result exceeds by far what was originally reported of Mr. Edison's instrument, and is done with a simple galvanometer, and without the assistance of a reflected beam of light and balanced resistances. I find that a great deal depends upon the thickness of the vulcanite strip. Thus the one I used for the above mentioned experiments weighs only 21 grains, but another strip of the same size, but thicker and weighing 35 grains, is not nearly so sensitive to heat. The needle of my galvanometer

procure a copy of Dr. De la Rue's paper on "Celes- description is necessary to make the construction grooves without the slightest injury to any part.