Графични страници
PDF файл

In determining the intensity of the from the surface of bodies, though magnetic force, a magnet was em- its intensity depends upon the incliployed to draw a needle to the hori. nation of the surface to the axis of zontal position. The magnet was the crystal; that the change in the then removed at an observed mo- angle of polarisation produced by ment, and the needle permitted to the interior force, depends upon the oscillate till the arcs became too inclination of the reflecting surface small to be observed. At every to the axis of the crystal, and upon tenth vibration, both the arc and time the azimuthal angle which the plane were noted. The azimuth compas. of reflection forms with the principal ses employed by Captain S. to de. section; and that the change in the termine the magnetic variation were direction of the polarisation depends made upon Captain Kater's improved upon the angle which the incident plan. The observations were gene- ray forms with the axis of the crysrally made upon the ice, to avoid the tal. great irregularities produced on March 11.-A paper by C. Bonny. board by the iron of the ship. The castle, Esq. was read, entitled, “ On results of the different classes of ob- the pressures which sustain a heavy servations were arranged in a tabu. body in equilibrium, when the points lar form.

of support are more than three." March 4.-A paper was read by Dr The author observed, that there is Brewster on the action of crystalliz. no method, purely mathematical, by ed surfaces on light. Malus has re- which the difficulties involved in this marked, that the action exerted up. problem can be surmounted; but by on light by the first surface of Ice- considering the circumstances unland spar is independent of the po- der which the pressure is usually gesition of its principal section; that nerated, we may be enabled to dis, its reflecting power extends beyond cover the law of its distribution, and the limits of the polarising forces of this law must always govern its prothe crystal; and that as light is only portional quantities and intensities. polarised by penetrating the surface. The paper concluded with an investhe forces which produce extraordi- tigation of the case when the numnary refraction begin to act only at ber of points of support is infinite, this limit. He also remarked, that or, in other words, consists of a line. the angle of incidence at which the or plane surface. spar polarises light by partial reflec- April 1.-A paper by Dr Brinktion is 56° 30'; and that whatever be ley was read, entitled, “ Results of the angle included between the plane Observations made at Trinity Col. of incidence and the principal section lege, Dublin, for determining the obof the crystal, the ray reflected by liquity of the ecliptic, and the maxi. the first surface is always polarised mum of the aberration of light." in the same manner. After stating After some general observations, the these observations, Dr B. proceeded author proceeded to consider the oto observe, that his experiments up- pinion of astronomers, that observaon the subject led him to draw dif. tions of the winter solstice have giferent conclusions, and seemed to ven a less obliquity than those of the indicate that the polarising forces ex. summer, -an opinion sanctioned by tend beyond the crystal. He also the observations of Maskelyne, Arashowed that the force of double re- go, and Pond, but questioned by fraction and polarisation originate Bradley. Dr B. referred this diffe



[merged small][ocr errors][merged small][ocr errors]

rence to some unknown modification prée, from which the water must conof refraction, and stated that he has tinue to accumulate until it deepers observed, at the winter solstice, that and widens the channel, so as to be the irregularity of refraction from come adequate to its discharge. To the sun is greater than from the stars this accumulation the author chiety at the same zenith distance; whence referred the peculiarities in the rise he inferred the necessity of paying and fall of the tides in the neighbour greater attention to the observations hood of the above-mentioned places. made at the winter solstice. The The formation of the coast, by gra, author next stated, from his own ob- dually altering the course of the tides servations, the maximum aberration between the South Foreland and the of light for last year to be 20.80%. Buoy of the Nore, from E. N. E. :o

Another paper was likewise read, W. N. W., occasions a gentle blend. on some New Methods of investigat- ing of the waters, so that there is a ing the sums of several classes of In: strong eddy about the Kentish Knock, finite Series, by C. Babbage, Esq. and a foaming ripple where they meet From the nature of the subject, this and proceed together. paper did not admit of being read in Ai this meeting a paper was also detail; but the object of the author read, by Sir E. Home, on the Ora of appears to have been to explain two the opossum tribe. methods of finding the sums of a va- A paper, entitled, “ A case of a riety of infinite series. The author Blue Child, with the Dissection," v3 stated, that results nearly similar to read, by J. F. Wood, Esq. This chili his own had been obtained by MM. lived twenty-one months. On re

. Poisson and Lagrange, but neither moving the pericardium after desti, of these mathematicians had explain- a large vein was observed descend ed the causes of the errors to which ing on the left side of the tboras, and their method was liable, or given a terminating in the right auricle of the method of correcting them.

heart, in which the superior vena ca April 22.- A paper by Captain J. va was also terminated by a distinct Anderson, R. N. was read, entitled, opening. The auricle was large, and “Some Observations on thé Peculia- the foramen ovale pervious. The rity of the Tides between Fairleigh aorta and pulmonary artery andse and the North Foreland, with an ex- from the right ventricle, the carity si planation of the supposed meeting of which was likewise large and strong

, ihe tides near Dungeness." After and had no communication with the some general remarks on the com- left except by a foramen through the mon opinion, respecting the meeting septum which divides the ventricle of the tides between Dungeness Point At this meeting a

paper and Rye Harbour, Captain A. pro- wise read by W. Morgan, Esq., eceeded to describe the peculiarity of titled, “ Observations on the Ner the channel at that point, and its very System of Diagonal Framing, intro sudden contraction between Dunge. duced into H. M. Navy by R. Sepness and Cape d'Alprée, and between pings, Esq.” (now Sir Robert Sep the South Foreland and Calais Point. pings.) The author approved highly In consequence of this contraction, of the principles of this celebrated the western tide, according to Capnaval architect, and pointed out the tain A., meets with a resistance in its great advantages arising from their course at Dungeness and Cape d'Al- adoption in practice.

[ocr errors][ocr errors][ocr errors]
[ocr errors]
[ocr errors][merged small]

: April 29.- A paper was commenced these important points. The results

by Dr Brewster, on the optical and of the author's numerous observaphysical properties of Tabasheer. tions and experiments were arranged

May 6.-Dr B’s. paper was con- in the form of tables, and consequent- cluded. The Doctor entered at great ly do not admit of being detailed. -length into the various properties of The general conclusion from the

this substance, and detailed Mr Me- whole was, that the composition of ron's experiments with the view of de- sea waters in all parts of the ocean is termining the power of tabasheer to very nearly the same, both in respect absorb different fluids, and of ascer. to the nature of the saline matters, taining the corresponding effects pro- and their relative proportions to one duced upon its optical properties, another; and that they only differ specific gravity, &c.

from one another, with respect to the May 13.-A paper by T. A. Knight, absolute quantities of salt they conEsq. was read, on the different qua. tain. In the course of the paper, the lities of trees felled in spring and following interesting facts were menwinter. From his experiments and tioned. Dr M. had been furnished observations, the author concluded, with specimens of sea water from that in order to give durability to the both the late Arctic Expeditions; and alburnum of oak, the tree should be on comparing the labels attached to barked in spring, and felled in the them, he found that in the Greenensuing winter.

land seas, the temperature, as ascerMay 20.-At this and the previous tained by Lieutenants Franklin and meeting a paper by Dr Marcet was Beechy, uniformly increased with the read, " On the Specific Gravity and depth ; while in Baffin's Bay, accordTemperature of Sea Waters in diffe- ing to the observations of Captain reat parts of the Ocean and in par- Ross and Lieutenant Parry, it was ticular Seas; with some account of constantly diminished. Dr M. also their Saline Contents.” The object found that specimens taken from the of this paper was to determine the surface were generally not less saline general properties of sea waters in than those taken from great depths, different parts of the ocean and at unless the surface had been lately different depths, with the view of as- thawed, when the quantity of saline certaining whether they differed from matter was found to be much dimi. one another, and in what respects. nished. In speaking of the composiAfter some preliminary remarks, Dr tion of sea waters, Dr M. stated the M. proceeded to describe the instru- important discovery of Dr Wollaston, ments which had been contrived to that they uniformly contained potash. raise water from different depths, or The proportion of this alkali present from the bottom of the seas when Dr W. estimates at somewhat less practicable, and which had been em. than the zooth part of water at its ployed in collecting the different common density ; and he supposes it specimens. The three great points exists in the state of sulphate. kept in view in the course of the ex- June 10, 17, and 24.- These three amination were their specific gravity, meetings were occupied in hearing their chemical composition, and their read a paper by Captain H. Kater, temperature, when this could be as- entitled, “. An account of Expericertained ; and the author gave a cir. ments for determining the length of cumstantial detail of the precautions the Pendulum vibrating seconds at attended to in the investigation of the principal stations of the Trigono

metrical Survey." The author com- posed by the author to be produced menced by noticing the reasons which by the granite existing in Mount Sor. induced him to undertake the expe- rel in Leicestershire. Captain & riments forming the subject of his stated that he had learned with plea present report ; and afterwards pro- sure, that M. Biot's results with receeded to describe the apparatus em- spect to the acceleration of the peployed. The operations at each sta. dulum between London and Unst a iion were then minutely detailed, greed with his own to within 0.6". and the results stated at length, and July 1:- A paper was read, on the illustrated by numerous tables. causes which influence the direction

For the latitude of London, the of the Magnetic Needle, by Captain length of the pendulum vibrating se. J. Burney, R. N. The author, after conds, on the scale forming the basis relating a variety of experiments, apof the Trigonometrical Survey, was peared to conclude, that the compass stated to be 39.13722 inches. is governed partly by polarity, which

For the latitude of Unst, 39.16939 he considers as created by motion, Portsoy,

89.15952 and the primary cause of the needles Leith Fort,

89.15347 pointing north and south, and partly Clifton,

39.14993 by attraction, which is inherent in Arbury Hill,

39.14043 matter; the former of which is conShanklin Farm,

39.13407 stant, the latter variable. On these The calculations of the latitude of principles the author attempted to each of these stations were then given explain why the needle is most liabk at length. The latitude of Arbury to be disturbed in high latitudes by Hill, which had been supposed erro- attraction, the obliquity of the plas

: neous, was found by Captain K. to be of the earth's rotatory motion to the correct. The whole was concluded horizon being here greater, and henc with some observations on the figure the polarity of the needle diminishes. of the earth.

At this meeting also a paper ** It appeared from this report, that read by Arthur Jacob, M. D. of Dubexcepting the allowance for the height lin, giving an account of a new met above the level of the sea, the error brane discovered in the eye. The in the vibrations of the seconds pen- author described a delicate transpa. dulum at any particular station did rent membrane covering the ester not amount to sth of a vibration, nal surface of the retina, and united which is about equal to the 400,000th to it by cellular substance. The pipart of the length; consequently that per was concluded by pointing out the amount of gravitation could be ihe best method of detecting and exdetermined to this degree of ac- amining it. curacy. Now this is so near as to The titles of the two following paindicate the different degrees of den. pers were also read, but from the na: sity of the materials constituting the ture of the subject did not admit ei substrata of the different stations in being read in detail. « On the The a country selected for experiment. ory of Capillary Attraction," byd

. Hence Captain K. concluded, that Ivory, Esq.; and “ on a New Merbod minute differences in density, indi- of solving Numerical Equations of cated by the pendulum, are often to all Orders by continuous Approxibe referred to irregularities of attrac- mation,” by W. G. Horner, Esq. tion : thus the sudden increase of The society then adjourned til gravitation at Arbury Hill, was sup- November.

ROYAL INSTITUTE OF FRANCE. motive caused the French Govern

ment to seize with avidity the opporIn the public sittings of the 22d of tunity offered, two years ago, of see2: March 1819, a notice was read by M. ing this operation, already so grand, 1. Biot, on the continuation of the la. extend itself towards the north to :bours undertaken to determine the nearly equal extent, in uniting with a 2. figure of the earth, and upon the re- portion of the same meridian, which ss.sults of the experiments on the pen stretches from the southern coast of 1 dulum, made in 1817, at the Shet. England as far as the Shetland Isles, celand Islands, by himself and others. to a higher latitude than St Peters

At first, it was merely known that burgh ; a portion which the scientific the earth was of a round figure, men of England have been now twen. e which was easily ascertained by the ty years occupied in measuring. is circular form which its shadow pre- In order to terminate this immense I sents when projected on the moon's arc, which comprehends almost the 5 disc during an eclipse. Newton af. fourth part of the distance from the

terwards discovered, by his calcula- equator to the pole, there remained no. baitions, that it was not completely thing, last year, but to construct some

round, but somewhat flattened at the triangles between the Shetland Isles poles, and protuberant at the equa. and Scotland, by the medium of the ior. The methods of observation, Orkneys, and to connect the operayet imperfect, have, after great diffi- tions of the English and the French culty, established this truth, which has at the point of junction, Dunkirk, by been at last 'obtained by measuring means of a system of combined opedegrees of the meridian under the rations, in which the instruments emmost distant latitudes, namely, at the ployed by the observers of the two equator and near the poles. The nations should be made to co-opeflatness of the poles was thus put

be- rate. yond doubt.

The operations prose- This last labour was executed in cuted for the last fifty years in France, the preceding autumn. MM. Arago England, Sweden, America, and In- and Biot went to receive, at Dunkirk, dia, have succeeded in determining the English observers, MM. Mudge, nearly its precise quantity. The mea. Colby, and Gardoer, who brought surement of the arc of the meridian with them the grand astronomical comprehended between Dunkirk and sector constructed by Ramsden, Barcelona, and accomplished with which they had made use of in all infinite precision by MM. Mechain their preceding operations : and the and Delambre, was the foundation up- French, on their part, brought one of on which the new system of French their repeating circles. measures was constructed. The desire At Dunkirk this fine instrument of communicating greater precision was, by the desire of the observers, to these results, caused this first arc placed within the marine arsenal. to be prolonged across Spain as far The English brig the Investigator, as the Balearic Isles *; and it became which bad conveyed it thither, was a part of an immense triangle above also to bring it by the docks to the the Mediterranean. In fine, the same place where it was to be employed,

Under the name Balearic, we have followed the ancient, and the latest of the modern geographers, in including not merely Majorca and Minorca, but Ivica, with its contiguous cluster of islets, of which Formentera, where these geodetical operations were prosecuted, is one. Ivica, however, with its dependencies, constitutes the “ Iles Pithiuses" of M. Biot.

« ПредишнаНапред »