Image provided by: University of Oregon Libraries; Eugene, OR
About The west shore. (Portland, Or.) 1875-1891 | View Entire Issue (Feb. 1, 1880)
February, 1880. THE WEST SHORE. 43 THE SOLAR ECLIPSE. OBSERVATIONS OF Till COAST SUKVBY PARTY. At the meeting of the California Academy of Sciences on Monday evening, Prof. (ieo. David- on, of the U. S. Coaat Survey, aaid that, ar heretofore, Capt Patteraon, the Superintendent of the Coast and Oeodetie Snrvev had eiven him permission to communicate to tho Academy the general facte obierved during the late solar eclipse. Then, with the aid of the blackboard, he described tho points of interest iu a very lucid manner. lie said: In the lato eclipso the cone of shadow was so small, from the apparent diameter of the sun and moon being so nearly the same the latter exceeding the former by only the two-hundredth part, that it mado it hardly worth tho while of astronomers to come here from differ ent plaoea to view it, especially as it took place so late in the afternoon. Heiug well acquainted with the topography of Monterey county, I chose the Santa Lucia mountains as tho best place of observation, that being the highest point for a hundred miles. There wore many minor difficulties to bo encountered. The mountain waa (1,000 feet high, and thero being no trail, we had to cut our way through the ohemisal. In the instructions for astronomers issued in 1878 for the eclipse of July of that year, it was eseoially mentioned that the Knglish anil American almanaos differed so that the estimated fat lis of totality differed three milos in location, was desirous, though tho arrangements could not be made, of having the north, south anil central points determined by different observers at different points, and thereby rectify minute errors that might cxiBt in the nautioal almanac, It is from our knowledge of the path of total eclipses from before Christ, that we are onahleil to check the secular changes of the moon. It formerly required long and intriuato calcu lations to determine the path of an eclipse, hut so many of the constant miautitios are now computed, that with most observers an hour or two of calculation, iuvolving merely quantities depending ou latitude and longitude, suffices to determine tho times of the beginning and ending of tho totality. Tu meet the requirements as woll as possible our party was equipped with a largo equatorial of li inch objective, one of :t inches, two of and one of 'J1,, all good glasess of high power and definition. These last qualities, as well as the quiet atmosphere and the high elevation which we sought to obtain, are necessary in order that the lirst and last points of contact may be accurately observed. Tho beginning all along the coaat was similar to what you saw here. The moon entered on the aun'i diak on the lower limb at about HO to the right of the vertical, and left the aun at a mint about 1(1 degreea from the vertical on tho li it. Ily the hiuh uower and large aiierture of my glass I was enabled to see the lirst contact of the limbs several aeconda anonor than tho others. Huth disks were real anil not spurious. Spur ioua disks arise from the undulations of the atmosphere, occasioned by unequal refraction, and in that case the body of tho sun or moon will not only apjicar too large, but there will be no well-dullned point of contact at any phase. Aa the moon advanced wo saw its contact with the sun's suots in three different groups. As totality advanced, several peculiar phenomena inhibited themaelvos. On account of tho slight apparent diameter of the moon over that of the aun, the cuaps became remarkably aharp. Ob servers at San Krancisco and Oakland saw these cusps rounded instead of sharp, on account of the irregular refraction caused by the differently Wtxd strata of the atmosphere. As the moon advanced, upon its edge became visible the lunar mountains. The darkness abort the disk of the moon was leu than the darkness of the moon on the aun, and yet the observers had failed to sea the moon t disk belore it touched me sun. Venus and Mercury hare both been teen pro Jocted on tho oorona before their transit s, and t has been supposed possible to see the dark body of tho moon before it touches the auu. My inatrumunt was ao arranged as to exclude all but ouo-tenth of the light and heat rays, whereby tho eye is proteoted from the effects of heat, etc. Tho approach can be detooted by spec troscopic methods before it quite touches, but uot as adarkliodv. As the two disks became ooneen trio, tho crusceut was remarkably prolonged, because tin- diameter ol thu mm hi waa apparently only 1 -'200th greater thau that of the aun. At that tune tho sun was passing into some cirrus clouds, and the points of the crescent were du- meatod. 1 was somewhat surprised at thu pro oniration of tho seiimeiit. which liuallv existed as a mcro lino of light 110 to -10 degrees in length. As it became narrow tho phenomenon of Daily's Heads, a serios of bright points of the sun hanging on the edge of the iiioou, caused by thu irregularity of the waves of light from atmosphurio vibration, waa possi ble. This phenomenon was not visible owing to the clear atmosphere, but tho liue of light was broken into dots and dashes, like tho .Morse alphabet ; tho dots 01 light marking thu depressions lietwecn the lunar mountains, as was proved by the fact that wlien one point of light iiisappeareu it inn not reappear, as in naiiy s Heads, but was gone for good. Thirty seconds is a very short time, uiiless you are hanging by the neck. That was all the time we had, how ever. Each one of us attended to his assigned luty. I was sucking for an intra-Mercurial planet, and had one chaiiec in a million. 1 hail prepareil a chart, with all the stars down to thu seveuth magnitude, and hopud to locate auy un known star by the coiiliguriitinu ol those about it. 1 was satisllud buforehaml, however, that the sky was too bright and that the uono of shade was too bright from a sort of re-illiimina- Hon, In consequence of this, the effect of tho eclipse was somewhat disappointing: theie was no black shadow creeping ovur thu eatth and the oeeau, as in a totality of throo or four minutes, but only a brown area advancing to us over thu ocean; and the atmosphuru was so light that we could make all our observations without arti- icial light. Upon the mountains we could not perceive the shadow's course at all. The want of depth of shallow was a disappointment to me, knowing that an intra-Mercurial planet would probably be invisible, and particular atteutiou was then given to tho corona aud tho bright Haines. There are four sketches of the corona made by our party, more consistent in their outlines than those by many morn skilled nb survurs with much inure time, It is impossible to describe the magnificence of the sight that the eclipse presented. Huge masses of red Haines burst out above the upper surface of the sun ouo-twolth or nuu-ttfteeiith of its entire di ameter in sizo, from .Mi, mm to 70,000 mile in hight. The lower limb of the sun produced a broken, jagged lino of rose-colored llame, extending around a third uf thu auu's oircutn ference, above tho apparent disc of the moon, and ooveriog miliums of miles iu area ; this reached 40,000 miles in flight. Tho llamca were visible for one or two aeconda alter the dissp pearance of tho sun, a rathur unusual phenom unou. After the re-apiiearaneo of the sun a change of conditions occurred showing the effect ol atmiispheriu causes. 1 he atmosphere Ihi came diaturbed and in watching the end of the eclipse the limbs ol the sun and moon were re markably disturbed. The smaller telescopes lost tho point of coutact lirst. As the moou weut off tho sun s disk, its outliuo appeared as a wavy line of black, that of the sun as a wavy line uf red, and It waa impossible tu tell the exact urn mont of their separation. Hail thu atmospheric vibration occurred at totality wo should havs had an exhibition from tins cause uf llaily's Heads. The phenomena visible at totality are the red flames, the chromosphere and the corona. A circle uf light around tho suu, in width equal to tbout one-eighth uf the sun's diameter, marked the lower part of the corona. Aa a rule, this is the only circle seen, but ou this occasion a sec ond circle leu bright was noticed outside the first. Outside tho chromosphere, which is the real atmosphere of the aun. the oorona stretched out to a diatanoe of about a diameter and a half iu the direct inn of tho sun's equator and to a smallor distance in the direction of its) axis. In the eclipse of I still, the oorona was sketch ed by aoveral observers but the sketches dif fered widely. On thti occasion at has boon aaid, the aketches agreed pretty olnaely, and two observers arc oonlldent that they aaw the corona lengthen and shorten rapidly. Aa on the previous occasion three observers, placed side by side, produced widely varying sketches of its form, it is not impossible that tho ooami eal matter of which the oorona ia composed may lie aubjuct to suddun changes. It has HN thought that the oorona and tha sodiaoal light may prove to have aome physical connection, ( specially as the latUr lies in the piano of tho auu's equator. The sodiaoal light was clearly visible on Santa l.ueia on the even ings preceding tho ucliise. The corona shines artly by its own and part ly by rellented light, ami ia therefore lie lievi'il to be formed partly of solid particles which reflect the light, while the bright lines of its speed nin indicate the presence of gaseous vapors. Tho chromosphere consists of the metallic va pors arising from the surfeoe of the sun, hut tho i In sphere proper ia only a oonitrative- ly thin stratum of ouo or two seconds uf arc, or from one to two thousand miles thick. Thu photosphere, or visible disk of the aun waa, during totality, covered throughout with the mottliuga known aa "rice grains. " Among these were scattered these larger ami mora crooked lines ol light known aa "faoulm." These rice grains and "faeulie are the apioaa of bodies of llsuio shooting up from the surfaoe of the photosphere, masses of llame winch, whan looked at edgewise during totality, appear as the iiiaguillcent "red-llames" which the spec trosuoiHi determines to lie incandescent hydro gen, magnrsium, etc. Tha photosphere la in uoiistant motion and spots ami groups of sputa aro generated by the matter Immediately around tin-in rushing sis with cyclonic action, and so quickly that while the sun t surface waa under haervatlon one of these spots waa divided III two. Varinua thenriea aa tu the constitution of tha sun have lieen put fnrth by Heoohl, Young, Kayo and ethers, but the one which appears to account most rationally fur thu phanomuiia praaentod ami fur the conservation of the eolar boat ia modilloalion uf that uf Kayo. Aecurdiug to this theory, tha aun it not a solid I .... I y . It has lung been evident to studsnts of physics that no solid body could continue to give out a constant and regular supply of boot and light to the whole anlar ay stem. No oheml nal act ion can account fur the heat, and actual lire would soon burn itself nut. Hut if tho sun is gaseous, ami onutiuually oontraoting, it hat b. en calculated that a contraction uf four miles iu its diameter in a century would be lulBultnt to account for the amount of constant radiant heat now given off from iU surface. The mass of the suu must thus consist of in candescent gases iu a highly compressed state, unable tu soldify beoause of the intents) boat caused by the constant contraction. Whan tins ..oi i. e tc. n . ease., liquefaction ur aolidlfluation will commence, and tha radiation of heat will rapidly diminish. In the corona there ia seen by the speotru i. ope the green liua called " 1 1,' I, which no eupiet a position diffsraut from that of any lino formed by tha known elauieuta of tba earth; thero ia alto present the helium line, prelimm arily to called. Several total eolipaat will ooour during tba next twanty years, aud will duubtlesa enable ua to solve much that it now unknown in solar physics. Tha next total ealipaa visible in tba I on. d -t.,t.-4 will be in the year l 'km. Tba longest poatible durttiou uf a total eollpet ia 7' M", those ooourring during tba next twenty years will giva us from throe to tlx minutes ol totality.