The New York Herald Newspaper, March 5, 1875, Page 3

THE ECLIPSE. Best Opportunity for Sun Study to Oceur this Century. Time and Track of the Sun's Total Obscuration. DIAGRAMS EXPLAINED. The Rose-Red Chromosphere and the Corona. SOLAR CHEMISTRY. The Sun’s Fiery Meteors and Meteorology. ECLIPSE EXPEDITIONS AND PREPARATIONS. The Novel Instrument for Attacking the Great Solar Problem. A Foreglimpse of the Earth’s “Dies Iree.” ‘The present year will be memorable in the ane nals Of astronomy. besides the great transit of Venus the phenomenon of a total solar eclipse— Probably the most favorable that can take place during this century—are among the celestial events toward whicn scientific attention has been eagerly directed, There are many grave problems of solar physics which, from time immemorial, have been uncer discussion, that can find solution only in spectroscopic examination of the eclipsed sun, Although the coming eclipse is not so rare ud so exciting an occurrence as the recent tran- sit there are pecuilar circumstances which invest At With unusual interest and importance. One of these is the fact that it will be observable Only at @ small number of land stations, and these lie mostly in the Indo-Chinese peninsula, witbin the little Kingdom of Siam. In this ancient na- Yonalty court astrologers and prognosticators have been long employed at trivial remuneration, and formerly were severely castigated on the falle are of their predictions. By tne roughest and crudest methods the Siamese astronomers-royal Dave been in the habit of calculating eclipses. Anc to them, we may well imagine, the greater acientific perfection of their European brethren, coming in their midst with the most magnificent and modern machinery of the star gazer, will be Anevent more impreasive than the eclipse itself, Although the phenomenon soon to be observed is now among civilized nations one o! scientific in- terest rather than popular terror, it has by no means lost its influence on the uneducated masses of men. Before astronomy had made known the cause of eclipses, their occurrence was regarded As indicating fearful deviatious from the ordinary course of nature. In the first year of the Pelopon- nesian war, whon the Athenian feet was ready to solar eclipse would have demoralized his men and marred his expedition, had not Pericles, its commander, been abie to explain the mystery. Bighteen years later an army, composed mainly of the same highly cultured and intellectual aAtue- Bian element, was lost from failing to move, ata critical moment, because terrified by an unex- Plained Inoar eclipse. History has preserved the instructive incident of how Columbus, sorely pressed by famine, relieved his wants and secured the i{ruits of his celevrated voyage by threatening the Indians that the taoon, then riding in serene majesty through the beavens, would be darkened on a certain day if they did not succor him. But while tne alarm bow excited by eclipses is confined to the untu- tored and unthinking, the many welcome such Phenomena and the world’s science is marshalling for new aud more brilliant conquests in the do- main of astronomic discovery. THE COMING BCLIPSE of the sun wil occur on the 6th of April next. The centrai eclipse begins on the earth a little southwest of Cape Agulhas (South Alrica), in longi- tade 99 deg. 19 min, 7 sec, east from Washington, Qnd in south latitude 35 deg, 30 mim, at 11b, 44m. Wasnington mean time. The first con- tact thus barely escapes the southern extremity of Africa ana the central line, along which the Shadow of the moon (interposed between the parth and sun) advances, runs irom southwest to northeast, Its track 18 now almost entirely oceanic, passing southeast of Madagascar and not Quite wrazing its southeastern extremity. Theace also missing Mauritius, where an able body of ob- servers could take the Geld, it fits rapialy onward, crossing the Equator in about lon- gitude 1¢6 deg. east from Washington, or avout 89 deg, east irom Greenwich. It then strikes (Fig. 1) through the Nicobar islands, in the soutnern part of the Bay of Bengal, and sweeps across Tenasserim, Siam and Anam, passing out into the China Sea and finally making its last contact on the open bosom of the Pacifica little northeast of the Ladrone Islands. The point Of this last contact ts about 147 deg, east of Green- Wich, in latitude 21 deg. 12 min, north, and occurs @t about 15). 12m., Washington mean time. To give aclearer idea of the phenomenon in question the diagram Fig. 2 18 presented. Al- though it is partiy seif-explanatory and graphic ally shows the PHYSICAL PHENOMENA OF THE ECLIPSE, (t may be well to notice the conditions under Which such an obscuration of the sun occurs, The aclipse of the sun ts caused by tho interposition of the moon between the earth and the sun, and When the conical shadow which the interposed Moon projects behind ber in space roaches the eaith, the pointa of the terrestrial surface on which it jails are completely deprived of solar light and involved in total darkness, Thoso parts of the earth covered by the mvon’s penumbra are, however, shrouded tn but partial darkness because from these parts only a portion of the light trom the solar disk ws intercepted. Accord. ing to the relative positions of the sun, moon and earth, @ variety of solar eclipses ia presented. If the apparent diameter ol tne moon happens to be greater than that of the sun, the obscuration of the great luminary will be total, ag in the approaching phenomenon to be observed in Siam, If the moon's apparent diameter be smaller than that of the sun. @ luminogs ring, formed by the unooscured portion of the solsr disk, 1s visible, and the ovlipse ia then annular—au instance which will occur and be observable at Washington on the 25th of next September, If the moon's cenire ja DOt exactly upon a atraignt line joining the sun's and the carch’s centre, the solar disk can, of course, be but partially concealed and the eclipse ig partials but when the contres of the three orbs 9 on tho samo acraight line, the result ia a central eciipac. The greatost possinie exc tho iunir above the solar diameter, an Been OY O terrestrial Obsei Vor, isonly tWo minutes | Ol BR degree, KO that tho greatest ecilpse that can ever or ani where occur can last only as long aa lt takea the moon to pags over about two minutes in her oroit, or about our minutes of our time, In such & cago the moon's shadow covers only A spat ebout 180 miles Lroad, though the penumbra (or parual shadow) may then darken &@ Oircular spot Ou (h6 earth's suriace having o diameter of nearly 4,900 miles, In dyure 2 tho sun's contre (S) 19 seen to be in& straight lime with (Ne imoon’s centre (M) and the earin’s Centre (12), God the reader ia supposed to be jooking down on tho earth's northern bemis. phote, The earth (marl @) 16 LOteting on ita | | tron ana the other heavy metuls, NEW YORK HERALD, FRIDAY, MAROH 5, 1875—TRIPLE SHEET. axis, and, at the same time, revolving in its orbit ground the sun in the direction (01), and the moon 18 revolving in its orbit around the earth in the direction (LN), On the latter’s coming in conjunction with the sun and earth tue solar raya, striking from W toward A are intercepted by the lunar crust, as also are the rays striking from Vv toward B. The dark shadow, or umbra, included between the letters A, B, C, D, is thus formed somewhat in the shape of a truncated cone, the base oi which rests on the nearer lunar hemisphere. Oa either side of the umbra, or full shadow, 13 the penumbra P, P, covering a much larger area of the earth's suriace, extend- ing from F to G, but only with a par- Ual eclipse of the solar light. In Figure 2 the moon Is represented as near ner perigee, or point of greatest nearness to the earth, which actually and exactly occurs on the 6.b of next April. Were she then to be in hor apogee, or at that part of her orbit mos#remote from the earth, her contcal shadow would terminate in a point above the sur- face of the earth and there would be no total eclipse, the observers in Stam seeing only a lumin- ous ring or annular eclipse. As it is, being near her perigee, the shadow reaches the earth, sbrouding in dense darkness an elliptical space about or exceeding one hundred miles in breadth, and this travels, as we have seen, with the motion Of the moon itself, with great rapidity. THE LAND TRACK OF THE ECLIPSE, The chart (Fg. 1.) exhibits the geography of the regions through which the central line of the eclipse passes. From this diagram will be feen the prominent points at which observations will be taken, These are the Island of Camorta, in the Nicopar group, the Isiana of Bentinck, near the mainland of British Burman, or Tenasserim Province, Mergui and Tenasserim, towns of the latter province, some point south of Bankok, and on the eastera side of the Indo-Chinese Peninsula, Hué, the capitalof Anam. At Kaikul, in Camorta Island, the totality laste 4m. 27s, the sun Deing av an altitude of 70 degrees, At Bentinck FIG. 2.---THE MOON Island the totality lasts 4m. 17s.; at Mergul, 4m. 6a,; at Tenasserim, $m. 57s.; at Bankok, 3m. 508., the sun ranging at an altitude of from 60 to 65 degrees. Within thes: four minutes of the sun in eclipse, by the ald of spectrum photography, it 1s believed as mach knowledge can be gained as ordinary solar observation would give in as many years. We have seen that the interposition of the moon between the earth and sun acts as acelestial dam to intercept the vast flood of solar light, and that the consequence is the dark cone-shaped shadow of our satellite. But, while the latter serves the purpose of @ transient dam, it cannot intercept the glare or radiance of the solar atmosphere—it- self a luminous fame enveloping the sun and rise ing hundreds of thousands of miles above the flery crust of that orb, The fuming atmosphere of the sun emits lignt which, during the eclipse, bursting over the interposed lunar barrier, reaches the eye and instrument of the eclipse observer; and it 1s this light which spectrum analysis so eagerly interrogates, in order to ascertain the CHEMICAL CONSTITUTION OF THER SUN. Th 1860, Mr, Warren de la Rue and the Italian astronomer Father Secchi were enabiea, by photo- graphs of the eciipsea sun, to satisfy themselves that the strange red prominences seen round the moon auring the total eclipse wore not of lunar origin, but belonged to the solar atmosphere. ‘This settled @ question that had been in dispute for @ century and a half, and paved the way for solviug the kindred and higher problem of the nature and composition of the solar atmosphere, or, more strictly speaking, the red prominences and the corona. The RED PROMINENCES, it will be borne in mind, We within and make up mainly the comparatively shallow part of the sun’s atmosphere ¢, ¢ the part which lies immedtateiy above the solar crust, or photosphere. This part of the sun’s envelupo is known aiso as the chromo- Sphere, or colored sphere, and may ve compared to the lower stratum of the earth's atmosplicre. But comparatively shallow as {t is, the promi- ences shoot up sometimes 70,000 miles, in the shape of a cone, or cimeter, and are of various col- ors, dcep red, pink and rich carmine and scarlet, Enormous as the chromosphere Is, it 1s, however, bata thin ligament tothe sun, as compared with the outer layer of {ts atmosphere, designated as THE OORONA, which may be likened tothe upper atmosphere of the earth, stretching indeflnitely outward into epace, far beyond the reach of instrumental ob servation or even muthematical computation, ‘The corona, a8 intimated, 1s separated from the photosphere, or light orb of the sun—tie orb vi ble to the naked eye—by the intervening chromo- sphere, and, as its spectra can also be photo- graphed during an eclipse, the utmost interest attaches to its chemical constitution. Before the ectipge of 1868 occurred—an event ever memoia- bie in the history of astronomy—Kirchof, by means of (he newly-invented spectroscope, had, approxi. mately, discovered the elements oj these solar atmospheres, and when the manifold eclipse ob- servations of that year were maturely diecussed they sustained his views generally, The result showed that the chromosphere, surrounaing tne bright, round, solar dis€ tnat we see every day, 18 an envelope composed mainly of glowing bydrogen gaa, into which are irequently Injected from the body of the burning sun (or photosphore) be ieath itand upou waich it reate, magnosium, sodiuw, and oveamoually ‘The “orignt linea’ observed on the lath oi August, 1608, tod, | unmistakably, thas the “red flames! or +rad | prominences,” forming the chromosphere, were | built up ol glowing oF incaudescoat vapor, gener. ated in the evor-fiery breast of the great lumin- ary, Bat now the question was, , WHAT 13 THB CORONA? | This halo of light, outside the prominence-eny lope or chromosphere, was the object of intense interest in tho next eclipse of 1809, during which the American observers, who had it ailto them. | selves, Made Humeroua and sploudid photographs | of the corona. In modern science, as in modern War, suc. eas bas become largely conditioned vy Wo instrumental periectness of the apparatus used FIG, 1.---THE LAND TRACK OF THE TOTAL ECLIPSE. TOTAL OBSCURATION. in the field. The needle gun and the rifled cannon have not been more decisive of modern battles than the spectroscope had been of modern as tronomic jaults upon the great problems of solar and stellar physics. Between the eclipses of 1868 and 1869, Mr. Lockyer, by the use of im. Proved spectroscopic apparatus, had been able, without the presence of an eclipse, and by mere lavoratory researches to verify tho rasults of the observations of 1863; and hence the observa- tions of 1869 were confined mostly to the exam {nation of the corona. The American observations ofthat year were not concl e, but they were of very great significance. This magic circle of silvery whiteness, conceniric with the solar orb, acd forming @ halo round the moon during the total eclipse, was shown to be self-luminous and in the main belonging to the sun, and not merely an optical phenomenon’ causea by the combined action of the sun’s rays, the moon and the earth's atmosphere, A jaint, continuous spectrum, free jrom dark linea, bat crossea by two or three bright lines told the important story that ithe corona, like the red prominence-envelope, is also probably of a gas eous nature, jorming & widely diffused stmon- phere around the sun, Especially was tne theory, previousiy held, that the corona may be due to a Innar atmosphere, entirely dissipated by the American obeervations, since, bad the theory beon true, the coronal spectrum snould have shown Frauenhover’s dark Jines, which was not the case, The conclusion reaoned by the Ameri- ean cbservors was then, in briei, that the corona is @ highly rarefied, selfluminous atmosphere of the sun, probably composed of the incandescent vapor of irop, at @ temperature exceeding 4,500 degree Bat the great qu Mot jet settled, and in 1870 another eclipse was obrerved in the Mediteranean with greater but indecisive success in the determination of the coronal constitution, Dark rays called ritte and streamers were seon in the coronal band, and from tne indications some astronomers conf. | dentiy concluded that @ part of it was due to tho solar atmos edvance was wiare of diferent phere, Another layers of important made in the next eclipse of 1871, when the corona was well photograpned, It was now established beyond doupt that it is a solar appendage, whose outer light is stronger in the violet and ultra violet parts of the spectrum than elsewhere, and that above the hydrogen en- velope, fainter and cooler hydrogen exists. The chromosphere below was, thereforc, proved to be alayer of brighter hydrogen and other vapors, Since the eclipse of 1871 # special investigation of the solar atmosphere has been progressing undor the auspices of Professor 0, A. Young, conducted at times at an elevation of 9,000 feet in the Rocky Mountains, where the airis so transparent that Many celestial objects, small and opscure when viewed from near tho sea level, become greatly Magnified and more perceptible, Professor Young has found that the vapor of the metal calciam, distinguishable only in a very clear atmosphere, is often present with magnesium in the sun's chromosphere. Hydrogen andthe metais of the aikalle and alkaline earths, metals of the tron class, and the presence of snoh metals as zino, aluminium and lead have been spectroscopicaliy indicated by th high mountain observations, Professor Yoong’s mountain observations were taken in the summer of 1872, at Sherman, the summit of the Union Pacific Railroad. He found the unclouded sky exquisitely transparent, and Multitudes of stars invisible at lower levels we consplonous, The spectroscope worked to groat aavantage, and be found 278 bright lines in the chromosphere, with occasional glimpses of very many more, Sulphur, strontium and ceriam were pretty conclusively shown to be constituents of the solar atmospne; aod probably eroium, zine, iridium and othor simtiar metals, His advai 0{ observation from this eminence we aging that this astronomer concluded the power Of tle glasses was increased by twenty-five por nd that tt might make a difference uf yours and Gecades In tle advance of astronomy if her new artiliory opened its attack upon the heavens trom the mountain top instoad of toe plain. THM CORONAL ATMOSPTIBNE, as Janssen proposed to call it, waa then conclu sively showWd in 2873 to contain hydrogen gas ata lower density than in the chromosphere, and that | astronomer’s observations went to prove that in the upper atmosphere of the sun there are solid and liquid particles reflecting the sunlight irom below, 8 vapory vesicles of cload or as smoke. The extreme tenuity of this outer balo may be tl- lustrated by the fact that comets have frequently passed very near and through it, and yet, not- withstanding the lightness of their mass, they have never fallen into tne sun. This tenuous cos- mical matter, emanating from the solar furnaces and composed of volatilized metals, indigenous in the soiar crust, is by no means in repose, but ceaselessly agitated by solar storms and eruptions from beneatb. The red flames or protuberances, whick carry the hydrogen to the enormous heights Of the coronal atmosphere, are peculiarly influ. enual in disturbing it, and may be supposed to | exert an influence analogous to that of a great volcanic eruption upon the terrestrial atmos phe! The enormous rapidity and violence of discharges from these SOLAR ETNAS have been startlingly stated py Professor Young. During the autumn of 1870 le witnessed a promi- nence streaming out from the sun, nearly verti- cally, to the height of 90,000 miles, as determined by @ time observation, Though at first very bril- | Mant, in thirty minutes it had faded away, leaving only @ few wisps of cloud. On the 7th of Septem- ber the same year, he saw and recorded an im- Wense solar cloud 100,000 miles long and 54,000 mties high. Having been temporarily interrupted in his | work, upon his return to it within half an hour he Was astounded to find the whole thing literally blown to shreds by an inconceivable uprush from beneath, Before his interruption, he had meas- ured the altitude of a part of thia prominence and found it had attatned 200,000 mules above the solar surface. The velocity of ascent he computed was 166 miles @ second or nearly 10,000 miles a minute. When we reflect upon such observed phenomena and others witnessed by European astronomers, in which prominences some 40,000 miles high have PASSING BETWEEN THE EARTH AND THE SUN. \\ \\ \ SAH LA Lip. been shattered to atoms in ten minutes, we get some (aint conception of the velocity and force of SOLAR WINDS AND STORMS, 1¢ 13 strongly urged by many distinguished sci- entists that these outbursts of solar energy have their correspondent agitations in the bosom of of the earth’s atmospheric ocean. The sun spot period of maximum number ard activity, it 1s claimed, has been shown to correspond witn the years of maximum frequency and tury of terrestrial cyclones, showing an intlmate connection be- tween our own and the sun’s meteorology. Mr. Charles Meldrum, of the storm-peaten island of Mauritius in the tropical belt of the Indian Ocean, has collated an immense number of meteorological and hurricane statistics and compared them with sun spots. He 1s quite confident that there exists & physical and casual connection between the two phenomena, and he has gone so far as to assert that the whole question of cyclones 18 @ question Of solar activity—‘‘many sun spots, many hurri- canes; few sun spots, few hurricanes.’ Whether this generalization be well founded Or premature, it is plausible enough to ascl- entific men generally to invest the study of solar phenomena with a novel and utilitarian interest which a purely philosophical inquiry might lack. As @ meteorological dogma tt will, no doubt, be rejecteqd by the majority of meteor- Ologists, seeing that terrestrial tornadoes are easily accounted for by those periodic alternations of heat and cold, dryness and humidity, high and low barometric pressures, caused by the sun's parent motion with respect to the earth’s equa- tor. But there can scarcely be # question that the sun’s varying activity, its vicissitudes of heat and electricity, its eruptive phenomena, within and beyond the chromospheric envelope, do modify the climate of all parts of the solar system. When it becomes possible to ascertain the number and magnitude of the forces at work inthe sun and upon its exterior (but mot till then), 1s it likely that the meteorology of our planet will be intelligently connected with that of the san, This romark, however, can hardly apply to the intercommunication of maynetio indica- tions. “The best authorities seem to agree that the greatest MAGNETIO DISTURBANCES in the earth’s atmosphere are due to terres trial, and not to solar or cosinical, agency. But Various observations attest, that great solar parox- yams correspond with the magnetio storms regis- tered, photographically, by the magnetic instru- ments at Greenwich, and this correspondence is Simost perfect as to time. It is, therelore, proba- bie that every outburst of the sun rece! Te sponse from the earth, and that the magnetio | impulse 1s propagated from the one to the othe! with the velocity of light, This fact evinces th: value of continuous and combined magnetic and sun-spot studios, THE MOMENT OF TOTALITY. In the diagram of a total solar eclipse (Figure 8) wo have the chief solar phenomena graphically delineated. ‘he dark central body represents the eclipsed sun, at the moment of totality, when the moon comes directly betweon the earth and the sun, The chromosphere is marked as a very shallow, ill defined envelope around the solar disk, as seon December 22, 1870, at Syracuse, by Captain G. L, Tupman, RM. A. This quasi. envelope has an irregular demarcation on its exterior edge, presenting @ serrated, billowy, | anat | that the great wor: Uneven surace, heaved up somewhat on its south: orn side (or apper side it appears in the dia. gram). The letters N., 8, B., W., show the north, south, and west limbs of the sun at the mo. ment Of total eclipse. The photosphere lies under the chromospheric eivelope and ia not represented at this of tho colip The corona is the Sell-luminous and extensive band or halo of tuin solar atmosphere outside of the chromosphere, The red fiames or protuberances of the chromo ephere, of course, cannot be shown on the dia. graw, but their relative place as to the corona | and the photospnere can oasily be understood, Wo have now given an outline of the many re Cent and latest discoveries in the aomain of solar physics, enriched, anit has bean, but only vy sow and fragmentary additions, at & lavish expendi (ace of totl, study aud material Fesources, it only | ia, ani | tne cold-b! remains to inquire how the knowledge now ha@ can be augmented through the approaching eclipse observations. THE PREPARATIONS FOR OBSERVING the April eclipse are hardly yet mature; but without such unfortunate weather as was ex- perienced in 1870, the Siam expedition will pa likely to secure the best photographic records ever yet obtained. Strange to say, the prospective credit of the April work, whatever it may be, wili belong, not to the Europeans, but to the King of iam, who has taken the tnitiative in inviting astronomers to his dominions and providing for their entertainment while there. On the 9tn of jast October His Siamese Majesty, througn hia private secretary, Buashakarawangse, extended this courtesy to the Royal Astronomical and Royal Societies and to any astronomers they might ac- credit to Lim, for the purpose of uti izing the coming opportunity, Other letters to other rociee ties and to triendly governmenta have, we believe, been addressed, Tne Engiish government bas ap- propriated about $5,000 to detray the expenses of its own eclipse expedition and to provide the suitable apparatus, so as to secure the fruit which has been so long ripening and 1s now ready t@ drop into the hands of science. The time inter vening before the eclipse comes off ia short; bat the Nicobar and Siam stations can be reached by fast steamers from Calcutta or Galle, connecting with the Mediterranean steamships navigating via the Suez Canal. The siderostats to be employed by the Englism have been constructed by Messrs, Cook & Sons, of York, who, tt ia said, have tmproved uponthe original model of the inventor. The arrangee ments are no doubt alreaay perfected, and the expeditionary parties on their way to Calcutta, The French government will be represented by an expedition under control of M. Janssen, thé well known astronomer, whose probavle deste Bation is Hué, Ina very recent letter to tue French Academy of Sciences, Mr. Lockyer, of England, writes that the English observations, im the Nicobar Islands aud Siam, will be directed mainly ‘to the spectra of the chromosphere an@ the coronal atmospnere, with the principal view to determine the chemical constitutton of the late ter.” The same line of inquiry will propably be followed by the French observers. The latest European intelligence from tnose ine terested in the eclipse observations states that Dr. Vogel, the well known Berlin astronomer, will Join the outgoing astronomers at Suez and Dre Janssen at Singapore. The Italians are also to be represented by Professor Tachini, who 1s already in Calcutta, ready to move to the eclipse stations, The British expedition sailed from Southamptom on the llth of February, in the Peninsular and Oriental Company’s steamer Surat, for Galle and Singapore. It is, we understand, a matter of regret to American astronomers that, Congress having made no provision for the United States to take part in the eclipse expeditions, no organizea party can be despatched hence iu time for the im portantevent. But the fullest preparations and instrumental equipments have gone forth with the European scientists, and all tne circumstances are auspicious, But, among all the circumstances which lend importance and give promise of suceess never before attained, to the forthcoming eclipse ob» servations, is the proposed application of the new instrument. THB SIDEROSTAT. It has been well and beautifully remarked thaq the barometer ‘has brought in sight a new coum try, and has enriched science, not only with new facts, but new principles.” The same eulogium may aptiy serve to characterize the destined ‘utility of the siderostat. Grand as tne resulta have been, which have been developed by the use of spectrum photography, the latter application is of very limited value unless combined with suck an instrament as the siderostat, which 18, doubt. less, to effect a great revolution in astronomical observation, The coming eclipse isto be the ob- Ject of its novel and special attack, and the prom pect is very exhilarating to astronomers. ‘The siderostat was devised to enable tne ob: Server to escape the inconvenience and often the impossibility of changing his position to follow the eye-plece of his telescope, when turned upon the moving sun or star, With the best telescopie mountings and arrangements which have hercto= | fore been employed, the observer is put trequently in the most uncomfortable positions, and his work subjected to those errors irreparable from the nervous handling of his glasses at the exciting and critical moment of tne eclipse. The ingenioux scientist, Foucault, the perfecter of the siderostat, aimed to give the equaturial the power of making the entire heavens pass before the observer witie out his having to disturb himself or to dispiace the instrument. The siderostat, as arranged by him, 1s, therefore, @ telescope fixed horizontally in am inyariable position, before which a plane mirror brings successively the various points of the 8&ye The whole rests on a brass stand, supported by three screws, with two levels and @ regulating azimuth movement. The plane mirror is cartied by a horizontal axis on the top of two vertical supports, which revolve round @ centre, the move, ment being perfectly effected by small wheels at the ioot of the supports. By the employment ofa CLOCKWORK MOVEMENT, the isochronous regulator of Foucault, placed at the foot of the instrument, communicates to the plane mirror mouon sensibly equai to the dk urnal motion, 80 that the heavenly bedies main tain invariable positions in the field of the hort, xontal telescope, in front of the spparatua directed toward the mirror. This clock move: ment, which has been applied to equatorials, ia periectly regular, and won for its inventor the grand prize in the mechanical arts at the Unk versal Exhibition of 1867, The apparatus gives | perfect steadiness in experiments for measuring the position of spectrum lines and ef the displaces ment of tne lines by means of large fixed speo troscopes, Its adaptability has been tested dum ing the recent piotographic experiments in connection with the transit of Venus, and with the greatest ease it combines with the observing telescope tne apparatus necessary ‘or the work of celestial photography for photometria Fesearches, The complete instrument, telescope and siderostat, placed in the plane of the merm dian, may also be regarded aso meridian instr ment, so that it is, perhaps, the most powerfal Weapon of modern astronomy; and, when de:tired, spectroscopes and photographic apparatus con La attached to the eye-piece of the telescope, of & size even larger than the telescope itself. The instrumental advantages with which asts'om omers will study the approaching eclipse, b.v¢ been maturing since 1860 with great rapiditK, and the promised result of the Siam expediting ‘will be the fruit and crown of the work so auspk clously commenced fifteen yoars ago. The exper whad in photographing celestial onjects ectrum photography lend an importance | to the present undertakings which similar eclipse A total eclipse of the sun is one of the grandest and most awe-inspiring sights it is possivie fer man to witness, “It is an awfal event,” says Mr Locxyer. “On ms in ® new world—a world filled with awiul sights and strange forebodings, and in which stillness and sadness reign cate ard the voice of man and the cries of animals hushea; the clouds are full of threatenings and put on unearthly hues; dusky livid or purp' we C] iowish crimson tones chase each other 0 irrespective of tne clouds. The very # aponsive and turns lurid rr All at once oon’s shadow comes sweeping over air an rth and ky with irightfal speed. Men look each other and Sele, nadie; ag ir an's light 1s lost.” No wonder was 3 ight Giver of the heavens 'pped by the Persian followers of Zoroaster, under ihe symbol of and in the once spiend! kingdom of the Peruy: Incas Se tn divine sacs ration. Weil might the poet write “Mew red?) tm Most glorious orb! that wert a worship ere The mystery of thy making was reveaied, hia sight blotted out of the heavens stil) eed ever must be, appalling; and jooded scientist becomes tremuloes wit! motion, Vreadful as th eraaie ta, the birth ined in medi@val song:— Dies ir, dies ile Solvet ag@clum in taville, which i# to coms upon tl th, when ite, ia closod, ite destiny consummated, and the aball be darkened, aad the Moon shall wi thdra’ ber shuning.”