about 23° west of the true north. The discovery of the fact was at first hailed as of immense importance to navigation; it was imagined the longitude of a ship at sea might be determined by the declination of the compass alone. It is said that Sebastian Cabot boasted on his death-bed of having this knowledge through "special divine manifestation." The idea of the early navigators can be readily understood. In 1492 Columbus discovered in the Azores a position of no declination, or where the compass pointed due noth and south, and it was imagined that the declination increased in a regular manner from this position. Suppose the compass deviated one degree for each 100 ⚫ miles east or west from this point, then the mariner could easily tell how far he was distant from the point by noting the number of degrees the compass has deviated. As observations on declination were multiplied, however, the hope of the early navigators was dissipated, for it was found that the phenomenon was exceedingly irregular; and if the points of equal declination were joined by lines, after the manner of geographical meridians, as laid down in maps, these lines were of an exceedingly irregular and wavy form, so that the declination of the compass at any particular spot could only be known by actual observation, and until the whole surface of the world had been mapped out the declination of the needle could not be used as an exact indicator of the longitude. In 1576 Robert Norman directed attention to the dippingneedle as a means of investigating the distribution of the earth's magnetism. This instrument measures, not the deviation of the needle from the true north and south line, but the inclination or angle which its deviation makes with the horizontal line, when it is free to move in a vertical plane. This method may be understood if we observe the behavior of such a needle when placed in various positions over a large bar-magnet. When at the centre it will have no dip, but be quite horizontal; but as it is carried toward either pole it will incline more and more, until it becomes vertical at the poles themselves, as illustrated on page 509. The middle point, where the needle is borizontal, may be termed the magnetic equator. Investigating the earth's magnetism in this way, it was found that the inclination generally increased from the equator to the poles, and sanguine hopes were entertained that the latitude might be determined by its means; just as similar hopes had been entertanied regarding the determination of longitude by means of the declination; but the same cause dissipated the hope in both directions-viz., the extreme irregularity of the distribution of the earth's magnetism. The lines forming the points of equal inalination were found to be as irregular as in the case of declination, and the magnetic equator was not a large regular circle coinciding with the geographical, but passed around the globe, sometimes north and sometimes south of the latter, and cutting it in two, or perhaps four, places, but not coinciding with it to any extent. Locally, however, the inclination may be, and has actually been, used by vessels in darkness or mist to determine whether they were north or south of a port they wished to enter. due mainly to the illustrious traveler Humboldt, remains to be mentioned. This has reference, not to the direction, but to the intensity, of the magnetic force at different parts of the earth's surface. If we cause a magnetic needle to oscillate backward and forward near a large magnet, we shall find these oscillations to increase in rapidity as the needle approaches the magnet or as the strength of the magnetism increases; and we know that the force increases in proportion to the square of the number of oscillations in a given time. Thus, if at one place of the earth's surface the number of oscillations is ten, and at another seven in the same time, we know that the force at the one place is to the force at the other as one hundred is to forty-nine. The results obtained by investigating the distribution of terrestrial magnetism by this method agree with those obtained by observing the declination and inclination, for while the intensity generally increases from the equator to the poles, the increase shows the same irregularity as observed in the other phenomena. The study of these various phenomena is greatly complicated by the fact that none of them is constant; they are all subject to incessant change, mostly of a regular periodic character: that is to say, the needle does not always exhibit the same declination or inclination, nor does the intensity of the magnetic force always remain the same at the same place. These changes are ceaseless and complicated, and their study is attended with great difficulty; but as the result of many careful observations, it appears that some of them depend on the time of day, some on the season of the year, etc., while others of a sudden and irregular character, when the needle is simultaneously affected over thousands of miles of the earth's surface, appear to coincide with the outburst of spots upon the sun's surface. In the northern hemisphere the north pole of the needle commences to move westward about 8 A. M., and continues to do so till about 2 P.M., when it turns suddenly, and moves back again toward its starting-point, which it reaches about midnight. During the night it repeats the movement, although on a smaller scale. So regular is the movement, that between the tropics the hour of the day may be known from the position of the compass-needle. Recently another movement, of an analogous nature, but which takes twenty-six days to complete, has been recognized; this time is just about the same as the sun takes to go round its axis. Another periodic movement seems to coincide in time with the eleven-years period of maximum and minimum sun-spots. Besides these whose periods have been recognized, there is a slow secular change, which has been going on for nearly 300 years, but whose cycle is not yet complete. Thus, in 1657 the compass-needle pointed due north and south at London; since then it has gradually turned westward, and in 1800 it pointed 24° 36' W., and it is now as gradually returning to the east again. The following table exhibits the character of the change, which is of the same nature as those of the shorter periods. Year. The By the aid of a dipping-needle, however, the positions of the north and south magnetic poles or points, where its direction is vertical, have been determined. north magnetic pole is found to be in lititude 75o 5', and longitude 96° 46' west, and the south pole in latitude 753, and longitude 138° east. They are not, therefore, diametrically opposite, and no straight line can be drawn between them and referred to as a magnetic axis analogous to the geographical axis of the earth. The two methods of investigation just described depends on the direction of the needle; a third method, however, One of Faraday's most brilliant discoveries-that oxygen gas, which composes about a fifth of our atmosphere, was really capable of being rendered magnetic, like iron-was eagerly seized upon as a possible cause of magnetic variation. He found that the amount of magnetism induced upon oxygen depends on its density; that again depends on its temperature, as it expands when heated, and becomes, of course, less dense. It was conjectured that, being expanded by the sun's heat, its lessened terrestrial The cause of terrestrial magnetism is not yet satisfac torily explained. It is evident that we cannot consider the earth as a body regularly magnetized, but rather as made up of an indefinite number of small magnets, the general result of whose action is directed north and south. Until lately it was supposed that only iron, nickel and cobalt were capable of exhibiting magnetic phenomena, and the magnetism of the earth was attributed to large masses of these existing in the interior of the globe; and, no doubt, there are large mountain masses capable of acting power-magnetic inductive power would react on terrestrial magfully on the magnetic needle. The researches, however, of Faraday, Weber and Tyndall have established the fact that all substances are capable of being rendered magnetic, and the phenomena exhibited seem to depend more on the physical state, as regards pressure, etc., than on the chemical nature of the substance. We may, therefore, suppose either that, owing to pressure, etc., the whole body of the earth is rendered magnetic permanently, or that it is rendered temporarily so by the inductive action of some body external to itself. There is one great difficulty in the way of such explanations, however, in the fact that all traces of magnetism disappear from all substances at a high temperature. Thus, iron at a bright red heat ceases to give the least indication of its presence. netism, and produce the variations observed in the latter. This ingenious explanation cannot be considered as more satisfactory than those already mentioned, as many of the phenomena to be accounted for do not occur at the time nor to the extent we should expect if the explanation were complete. Recently Professor Balfour Stewart has suggested another possible mode of the sun's indirect action. We know that if any body is moved across magnetio lines of force electricity is developed; and he says that the sun's heat causes convection-currents in the upper regions of the atmosphere, and these currents, cutting through the lines of force of the earth's magnetism, develop electricity, which reacts on the earth and produces the variations of the magnetic elements. ghThere is no doubt the sun's heat may, and probably does, affect the condition of the earth's magnetism in the indirect ways we have noticed; but no one of them, nor all of them together, seem to offer a satisfactory solution of this very complex problem. They offer no explanation of that slow secular movement we have referred to as having been observed since 1580, and whose cycle is not yet completed. As the interior of the earth must be at a very high temperature, it is difficult to understand how it could become magnetic, unless the great pressure modifies the action of heat on magnetism to a large extent. Many theories have been advanced to account for the variations in the magnetic elements of declination, inclination, and intensity which we have noticed, but none are satisfactory and complete. It is very evident, however, that in this, as well as in many other of the grander phenomena of nature, we must not confine our attention to the earth itself, but must consider the action of external bodies, and especially that of the great centre of the solar system. The coincidence in time of many of the variations with solar phenomena irresistibly leads us to attribute to its action much of what we observe, and we shall point out one or two ways in which that action may be exercised. First, we may suppose the sun itself to be a magnet acting inductively on the earth, and, of course, his varying condition, distance and relative postion, would produce corresponding changes in the earth's magnetism. To this explanation there are, however, great objections. From the fact we have mentioned-of a high temperature destroying the power of magnetism-it seems almost impossible to conceive that such a body as the sun can be magnetic; and, besides, it has been proved, from a mathematical investigation of the subject by Messrs. Chambers and Stoney that the variations observed in the earth's magnetism cannot be accounted for by the magnetism of the sun or moon, supposing these bodies to be magnetic. It would seem, therefore, that the sun cannot act in this direct manner. It may act, however, indirectly by means of the heat which it radiates toward the earth's surface. If we take a ring composed of two metals-say iron and copper-joined at two points, and heat one of the junctions while the other is kept cool, we shall find that a current of electricity will circulate round the ring. Now, we know that a current of electricity passing in this way acts exactly like a magnet. It is supposed that the sun acts in this way on the earth as it revolves, causing currents of electricity to circulate on its surface, producing magnetic action. These currents have been proved by observation really to exist, but on measuring them accurately they are also found totally inadequate to explain the phenomena observed. There is also a difficulty in the way of all heat theories in the fact that there is well-marked variation in the earth's magnetism, due to the moon's influence; and as the heat from that satellite is quite inappreciable, it seems impossible that the explanation sought can be found in that agent. It must be admitted that our knowledge of "terrestrial magnetism" is confined entirely to the observations made in various parts of the earth, and these are by no means complete. We have not as yet mapped out the distribution of the earth's magnetism over its whole surface, but only at isolated stations. We can but hazard a probable conjecture as to the cause of the magnetism itself; but as to its variations, we must confess that all our thecries f.ll short of a complete explanation. The study of the mysterious movements of the compassneedle has thus led us over a wide field of inquiry; it has shown us that the earth is, indeed, magnetic, but presenting the phenomena of an indefinite collection of small magnets irregularly distributed rather than those of a regular large magnet; it has shown us also that the magnetism is subject to incessant wave-like movements, some of them taking hundreds of years to complete and others only a few hours. We are obliged to confess our inability to unravel all the mysteries disclosed to us, but we are urged by the attractiveness of the inquiry to pursue our investigation. We feel assured that the sun is in some way connected by a magnetic bond to this little world of ours, as every movement he makes or outburst that takes place on his surface is instantly registered by the tiny needle. Possibly, there may be some hitherto unrecognized form of solar energy yet to be discovered by the student of science; but whether this be so or not, the close connection, if not absolute identity of electricity and magnetism, the probability of light being a magnetic phenomenon, and various other matters, render the inquiry full of promise, Owing to its practical value in navigation, many governments have lent their aid in investigating this subject, and numerous observatories have been established all over the world, where thousands of observations are made every year by competent workers; and it cannot be long before COMPASS AND CAPSTAN. nature will yield up her secret, as she always does, to persistent and well-directed effort, and then another field will have been wrested from the region of the unknown, and added to the ever-increasing domain of physical science. THE MARINER'S COMPASS AND NEW ADJUSTER. The manager of a number of iron steamships once remarked: "Compasses in iron steamships never are, and never will be, correct, and I do not want the compasses of my ships to be so. I forbid my captains to suppose it possible, as they would become careless." There are So many causes for compass errors, that it is a wonder more marine disasters do not occur. Even when correctly adjusted before leaving port, it is a common matter for a compass to increase in error until it varies from four to six points. Captain H. O. Cook, for many years an officer of the British Navy, has devoted nearly twenty years to the investigation of this subject, and has at length succeeded in devising an apparatus by which a compass may be readjusted at any time and place. Recent experiments have been made in presence of officers of the United States CAPTAIN COOK'S NEW COMPASS. THE AZIMUTH INDICATOR. navy, the revenue department and the mercantile marine, and the device met the fullest approbation. The instrument has the appearance of a compass, but has neither magnetic needle nor swinging card, but is simply a mechanical and scientific instrument, with a movable gnomon adjusted to each latitude. The degrees are cut on an outer circle, just as an azimuth would be; an inner circle is marked with the variations and declina tions. A movable disk is set by a table, calculated for the hours and minutes, and when the sun passing over the gnomon cuts the edge of the movable disk, the shadow gives the true north, and the compass can unerringly be adjusted therefrom. Another arrangement which proves the accuracy of this is likewise attached; and at night the stars can be also observed, and the adjustments made from one of them with equal facility. The ease by which it is operated and the substantial simplicity of its construction are its chief merits, while its perfect accuracy in results must convince the most skeptical of its utility. THE EDITOR'S OPERA-GLASS. THE "nut-brown mayde," October, finds us at the end of a very hot Summer. Never did the pleasure-seekers by the sea suffer so much, and even Newport was very warm, The first part of the season was virtually ruined by the heat; the latter part rendered delightful by the coolness. The President's visit to Governor Morgan was a splendid event for even Fashion's high abiding-place, and there are a thousand reasons why society should greet President Arthur with much distinction, for he is making the social atmosphere of the White House most attractive by his own entertainments and highbred courtesy. As the anniversaries came about, all reflecting people remembered the effect produced upon Newport during the sad Summer of 1881 as Garfield lay dying. How different the fates of the two men! Over one, destiny held a pall; The one over the other, the purple canopy of success. was called to martyrdom; the other to triumph. What seer could have foretold that at Chicago! Congress sat late, nor left a very brilliant record behind it. No body of representatives were ever so severely criticised. Especially do the naval officers reprobate that Bill which made so many of them lose years of promotion. The gallant Captain Selfridge, of the Torpedo Station, is put back for six years-a most undesirable event. The death of General Gouverneur Kemble Warren stirred the hearts of the people as few events have done since the war. He was relieved of his command on the battle-field by Sheridan, as it must be remembered, and, as he thought, most unjustly. Indeed, the world thought that Sheridan acted hastily. Since that day the proud soldier sought redress, but in vain. He worked, earned money, lived but for that purpose. A highly educated officer, most thoroughly acquainted with his profession, he was placed after the war at the highly desirable post of engineer-officer in command of the Department of the East, with headquarters at Newport, in a romantic old mansion in Newport, where Washington received Rochambeau. Here, with an attractive family, a delightful social position, General Warren seemed to have entered upon a happy and useful life. His great professional skill brought him in fresh triumphs daily. But the wound rankled. He was the slave of an idée fixe, Restoration to his rank, the wrongs of eighteen years, and Light" comes down upon us severely, quoting the righted, the apology of his superior officer, all were his Atlantic Monthly, the New York Nation, and, we are sorry to due, he thought. Finally, after years of waiting, expense, say, Mr. Lowell, as amongst the disparagers of our nationtrouble, courts of inquiry, he failed. He died of that old-ality. He takes his descriptions of American social life from fashioned malady, a broken heart, and now the country some town near Denver, which cannot be held as typical, says, "Alas! poor Warren! he asked for bread-they will and while scolding, denouncing, and vilifying American give him a stone." It is one of those pitiful cases where civilization, he says, demurely, that he is only "holding there is no one to blame. But, oh! the pity of it! a friendly conversation with American lovers of human life." This should for ever shut all doors against Matthew Arnold in America. Emerson said of an Englishman, "When he speaks directly of the Americans, the Islander forgets his philosophy and remembers his disparaging anecdotes." Mr. Arnold even enters into other and less philosophical statements. "A community which can barely find time for sleep or meals; that men have their hats tipped at every angle except the right one, and their feet anywhere but on the floor," etc., etc. (This from a country which has sent us an Oscar Wilde!) All this reminds us of an anecdote which had much interest for us at the time. An American lady went to the "Zoo," on a Sunday Over the water, one listened amid the Summer days for the guns which opened on the Aboukir forts, which reechoed to our shores before they began!-such are the mysteries of Time and the telegraph-and burned with indignation over the case of Mr. Dwyer Gray, in Dublin. The high position of the gentleman, and his good character, seems to have been so thoroughly established, that he should have been pardoned a much more heinous offense than the disparaging of a drunken jury. But whom the gods would destroy they first make mad, so we cannot but dread that the vengeance of the gods is bespoken for those who so misgovern and misunderstand Ireland. RECENTLY DISCOVERED CANALS IH THE PLANET MARS.- SEE NEXT PAGE. Miss Fanny Parnell, a most interesting but misguided enthusiast, died in America since our last glance at the world. The Parnell ladies are all interesting, and have much of their old American grandfather, Commodore Stewart, in their veins. But the wrongs of Ireland have driven them over to Communism, and one regrets to read that Miss Fanny Parnell consorted with Louise Michel, in Paris. She was a poetess of no mean ability, and a noble woman. It is not the least painful side of the wrongs of Ireland that they had nearly driven such a woman mad. As for Mr. Gray's sentence, the Freeman's Journal remarks: "It is absolutely unparalleled. He only received notice of the nature of the proceedings against him on Tuesday evening, and was without any time to prepare his defense, which would probably have consisted of affidavits sustaining the truth of his published assertions. If his imprisonment tends in any way toward the reform of legal abuses or the greater freedom of the press, he will cheerfully endure it." When we read that this gentleman was taken to jail between a tremendous hollow square of mounted scarlet English soldiers, we do not wonder that Ireland writhes. All these mistakes should make Matthew Arnold more lenient toward America, and yet the author of "Sweetness | He afternoon, with Sir John Bowring, twelve years ago. When the lady told him that every well-dressed woman he saw was an American, and that all New York imported French fashions, the old Chinese scholar looked amazed. But to English misappreciation of America we must learn to submit. There is no balm in Gilead for that. Prince Bismarck, meantime, discourses thus of Austria: "Austria will have to share the dangers created for Europe by the connection between Russia and France, and must avert them by timely sacrifices by either making concessions in Italy for advantages to be obtained in Germany, or else strengthening herself against attacks by treaties with other Powers. I believe she will choose the RECENT PROGRESS IN SCIENCE RECENT DISCOVERIES IN THE PLANET MARS.-An intended first alternative, and that she will try to gain Russia's con- | Belonging to the "Brahmin class," he was always the Austria will friend of the people, and in the close of his eighty-five fidence by a personal change of ministry. only in case of utmost necessity avail herself of our or of years a noble and a lovely career of unblemished usefulness is ended. English support. If she should end avor to make us guarantee her foreign possessions by new treaties, I do not believe she would use such a treaty for any other purpose than to parade it on the diplomatic field to her advantage and to our injury. Even supposing that arrogance and hatred should allow the Vienna Cabinet to ask for English assistance, or to have the hereditary imperial provinces protected by Russia, Austria is, on the other hand, even strengthened by an alliance with us and with England, too cautious to engage in a serious struggle against France and Russia if it can be avoided per fas et nefas. She will consider the party of the Teutonic nations too weak for her to join, and, in my opinion, she will be right in this respect. The whole A concession! Proud Prince Bismarck! European world is thus by the ears, and we see nothing for any of them, or all of them, but trouble, expense and war. Tant mieux pour nous. All the singing-birds, disturbed by conflict, are coming over here. Nilsson and Patti, and even Mrs. Langtry, too! and we are to have the first represent ation of Gilbert and Sullivan's new opera on November 7th. A gay and prosperous Winter seems to be the outlook for New Yorkers. article, of which an announcement appeared in Nature a few weeks back, on the topography of Mars, as delineated for the second time by Prof. Schiaparelli, at Milan, during the opposition of 18.9-80. has been anticipated, and in part superseded by information which has been received relative to the more recent discoveries made by him in the beginning of the present year. Pending the preparation of a fuller and more detailed memoir, he has published a preliminary notice, read before the Academia dei Lincei, on March 5th, and accompanied by a photographed drawing of the planet's surface. The results are of a very remarkable and unexpected character; and as through the courtesy of this distinguished observer, the notice and photograph have been placed in my hands, I am induced to reproduce the latter, which, though provisional sketch), will give a sufficient idea of the marvelous not pretending to minute accuracy (the original. in fact, is only a duplication of the so-called "canals." which, between January 19th and February 24th, in about twenty instances, unfolded itself progressively under the observer's eye. The discussion which took place at the late meeting of the Astronomical Society, so far as my information extends, substantiated strongly by independent evidence, the existence of these long, narrow streaks, some of them even in positions where they have not been delineated by Schiaparelli: but their duplication by similar and parallel lines does not seem to have been elsewhere noticed Some difference of opinion may possibly be expected concerning these strange appearances; and the consequent enfeebling (to say the least of it) of the long-admitted terrestrial analogy may be to some minds, unacceptable; but the established reputation of the observer demands, at any rate, a respectful attention to his statements. It may be preferable to suspend a more detailed account till we receive a full elucidation of the subject in the memoir, of which we possess only a preliminary notice; for the present it may suffice to mention that he found the atmosphere of Mars apparently clearer than in 1877, and was thus enabled to recover the markings then detected more satisfactorily even than in 1879-80, and to confirm the general accuracy of his two earlier charts; while the concise, but very clear intimations that he has given, as to the variable brightness of some great regions, the progressive enlargement on one side, since 1879, of the "Kaiser Sea" (his Syrtis Magna), the brightening of certain supposed continents or islands toward the limbs, the confirmed existence of oblique white streaks, the unfolding of minute labyrinthine detail, and the continuous development already mentioned, day after day, of the collateral lines which double the so-called "canals," and extend with them ordinarily along great circles of the sphere all these, and similar announcements make us anxiously desire a more ex It is to be hoped that we may, before another year, receive our promised statue of Liberty, by Bartholdi-a generous gift from France, asking us only to raise a pedestal. It is so enormous that the sculptor asked a The banquet was party of friends to dine in the thigh. successful and unique. The guests walked in by the right toe. One laid himself down comfortably inside a toe. Ladders conveyed them all the way up the calf, and finally deposited them where a temporary platform had been constructed. Soon they expect to enjoy a banquet in the head. Those travelers who have been so for tunate as to travel up the colossal statue of Carlo Borromeo, on Lake Maggiore, will remember the vast sensations enjoyed in that immense figure, and the beautiful pros-tended and detailed communication. For some of these most repect from the colossal eyes. Fashion has made a step backward; all the new gowns are made to lace down the back. The lovely Princess of Wales will wear only long dresses. Her walk is said to be more graceful in consequence. "A rapid, gliding step, so different from the springy, Dutch doll step that has come in with short dresses." The Autumn coolness has brought back the pretty fashion of white-silk waistcoats under tweed jackets. Buttons with impressions from antique seal-rings, in graduated sizes, are the most elegant. Some hunting Dianas wear buttons with foxes, heads, horses, stirrups, dogs, whip and spur, and jockey cap. The button! always the button, an important connection between the waistcoat and the color of the jacket. Red geraniums and white chrysanthemums-any yellow flower that can be found-and golden-rol and aster are the fashionable bouquets for October, The appointment of W. W. Astor, Esq., for the Roman mission has met with universal favor. Mr. Astor is a very good linguist, although scarcely rivaling the extraordinary capacity of Hon. George P. Mars', his predecessor, who spoke twenty-eight dialects; but Mr. Astor has much knowledge of foreign life, has a large fortune, a beautiful wife, and every social consideration in his favor. New York has had to mourn the loss of a most distinguished, valued and charitable citizen, Frederick de Peyster, Esq., who died calmly at the advanced age of 85. Mr. de Peyster has held more offices in literary and charitable institutions than any man except General Dix. markable appearances parallels may be, to a certain extent, pro- SIGNOR BONCELLI, of the Italian Parliament, has devised a simple and practical method of voting by electricity. Each member of the house has in front of him a metal plate bearing his name or number, on which are three buttons marked respectively "Yoa," "No" and "Abstain." The buttons are connected with a central printing apparatus, which prints in three separate columns the yeas, nays and abstentions, according to the button touched by the members, while, with every addition to each column, the sum of the votos in the column is automatically recorded." THE proportion of salt in the water of the ocean varies greatly in different localities. M. de la Grye has made a series of obser vations on the subject, in which-among many interesting results he has found that the saltness diminishes rapidly as a coast is approached, due, probably, to the freshening by rivers discharg ing into the sea. The salt also lessens on the approach of icebergs These facts would seem to have an important bearing on navigation, as in bad weather tests of the saliness of sea-water might enable the mariner to avoid running into unseen coasts or icebergs. DR. L. RICCIARDI has analyzed six specimens of the lava ejected from Etna in 1669, taken at different depths of one and the same stream, and in the same perpendicular plain. He found the only difference to consist in the different proportions of iron in the highest stage of oxidation. |