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The Transit Of Venus

The Transit Of Venus image
Parent Issue
Day
26
Month
February
Year
1875
Copyright
Public Domain
OCR Text

A oorrespondont of the Alta Califoria was a niouibor of Professor Watson's jarty who were sent by the United States Government to Peking, China, to bserve the tranait of "Venus. The Alta eueived his lettor, which was dated December lOth, by tho last China mail. Ie writes as tollo ws : Tho eventful day has come and gone- ho day we have buen so long looking 'orward to. Venus has passed over tho un's face, and the world can know how ar it is trom the " rulor of the planetary system." In this distant city, unconmictüd by the telegraph and with ut a weokly mail, we wonder how our jrother-laborers have fared, and what ïas been their success. Have they seen as much as we have, or have they been esa fortúnate 'í How we envy those who have had a clear, uninterrupted view of the whole transit. But we have much to be thankful for, and although the Goddess of Beauty was somewhat coy and capricious, she removed the veil 'rom her face often enough to let us admire her beauties. We have rendered a good record and a valuable one, and are satisfied. OUB PREPARATIONS. We arrived here September lGth, and with no delay solected a situation, built piers, erected houses, and put our instruments in position. Our fust time observations were taken on September 3Oth, and from that date on we have had an unexpected succession of clear nights, having observad fifty times. Photograpus of the sun were taken every week and daily for a few days preceding the transit. The inclination, direction and length of the axis of the photographic telescope were very frequently accurately determined. This telescope, be it understood, does not answer the common definition of that term - tube is altogether lacking, the rays from the objeot-glass passing throngh air protected, in our case, from distributing influences by a long structure of matting. Tho mirror through the object-glass to the photographic sensitive-plate, which is in the photographic focus, forty feet away, making upon it an image of the sun four inchea in diameter. Observatious of the niagnetic dip, declination and intensity have also been made. ARTIFICIAL TRANSIT. A week before the transit occurred we observed an artificial transit, so as to accuatoni ourselves to the different appearances. The apparatus consisted oí a glass slide, having upon it a smull tin foil representation of Venus moved by clockwork over another glass plate oovered with tinfoil except in the center, where there was a circumference of the proportionate size of the sun, which Venus iutersected at the proper angle. The edges of both were sharp, the niotion the same, and the appearance was as inuch as possible similar to the real affair. This was placed in front of the object gla6S, between it and the photographic house, and the mirror reflecting the sun threw it through the object glass and gave a uniform bright illuniination over the iinitation sun. This was observed trom the pier of the photographic plate-holder, and the times were noted by the observer on his chronometer, while spriugs falling off the sliding plate at the times of the four contacts, gave by their snap notice to the observer stationed there, who also took tho time from his chronometer. These two times being afterward compared togethor, the difference of the observed from the real times could be readily seen and the resulta attained showed very gre#t accuracy. THE PRECEDING UAY. Tuesday morning the sun rose through a low haze, and the whole atniosphere was covered with white clouds which gradually formed thicker, until at ten o'clock the sun was all but hidden ; and so it coutinned all day, only occasional flashes being visible. Evejything had to be looked at carefully, nothing overlooked - the smallest thing might créate confusión; and, in in reality, came near doing so, though most unexpectedly and most unavoidably. Tuesday night a light breeze sprang up and swept the sky clear and the stars shone out brightly. We observed time before miduight as usual, and went up again at four o'clock and observed till six - then leaving everything as it should be and seeing that all was right about the different instruments we walked hoineward on THE EVENTFUL MORNING. And as we saw not a cloud in the sky, in the darkened gloom, we feit that we were to be well rewarded for our labora. But as the sun came uearer and nearer the horizon a few light, flakey cloud were visible, and he roae shining bright ly, though through a slight haze, whic] oontained for ua we did not know whai We could do nothing, no use to borrow trouble - what was to be was to be - and we had done our duty in the prep arations. A hasty breaki'ast was aoou over and all hands on their way to th station. As we walked along we ooulc see the clouds gather and gather, auc as they rose higher and higher, ou hodes went lower and lower. At Í o'clock, a half hour before the transi begran, the sun was a mere white blotch in the sky. The sound of preparation was everywhere audible. Everything went on as if it was all clear. The programine proposed would be carried out. Prof. J. C. Watson, Prof. C. A. Youug and T. P. Woodwurd were to observe the fours contacta telescopically and carefully note their times and, in the intervals, to assist in the photographic house. Prof. Young had looked forward for years to uaing his speotroscope on the first contact, but the first light clouds made him abandon the idea. The photographers, W. V. Hanger, B. J. Conrad and E. Watson, were to make as many pictures as possible throughout the whole transit - two hundred if the day was clear and everything went well. Dr. Dudgeon and the Rev. Mr. Collins had kindly volunteered their assistance in the photographic operations, and our thanks are due to theni for their almost invaluable service. Now we started the chronograph to record the times of taking the exposures- but some circuit failed to work, although all right only tliree hours before. A search failed to show the break. A skurry here and there. The break, though annoying, was not an important affnir. Necessitates some one taking the time accurately in the photographic houso. Five minutes bofore the time the sun showed himself a little. No time for words uow. Every man at his post. The observers were peering anxiously through their telescopes, and the photographers in the dark room awaiting the signal to exposé the first plate. The computed time came and passed, but not until a. minute afterward was the riliST I'AINT NOTCII fSeen in the outline of the sun ; but this grew aud gew until Venus made herself well apparent. In half an hour she was almost wholly eutered on the sun's disc, and again was ehe carefully observed for the time when the first strip of light passed between her and the edge of the sun. There was a slight atmospherio disturbauce at tho time, the suu being viewed through hazu, which rendered the observations difficult. Meanwhile the photographtus were busily engaged exposing platos, one following the other at the short intervals of a minute and a half. Their joy at first seeing the impression of Venu was like that of Coluiubug whtm he iscovered America. When they had )hotographed for a littlo over an hour ie unwolcotue cry of "clouds," came rom the outaide, and observations had ,o bo suspended. Now, indeod, the ano soemed hopeless - tho olouds had 'orined so solidly that even tho position f the sun was no longer discerniblo. We occupiod oursolves in searching for bo brokon circuit, and finally found be broak, which we discovored had oon caused by acooliecarelesöly wheelng a load of water over the wiros which were laid on the ground. So the hronographs were all right again, anil we were prepared for any emergenoy, hough we had almoat givon up hope. About half-past one, an hour bofore tho lose, the UN UNEXPECTEDLY MiOKK ÏIIUOUGH he clouds and shone more brightly ;han in the forenoon. You eau war ant that we were not long at reoommencing photographing and we kept on ;o the end, grinding platea out at a minute a quarter intervals. The seeing was much improved irom the morning, and the obsorvations wero proportionately better. No " black drop," about which so much had been said, was visible at any time. The times of the last two contacta, when Vt;nus just touchos the outside edge of tliosun, aud when she finally leaves it, wore found to be a minute earlior than the time computed. This, combined with the morning results, show that a wrong ue was assuuied for the sun 8 diameter. That used by the French made a differenoe of three minutes. We wero aslo ed to infer that the times of the external contacts depended upon the power of the telescope- the higher power seeïng Venus sooner or later as the case may be - our resulta giving almost exactly proportional differences. THE RESULT8. We observed all four oontacts telescopically - all by two, and two by three observers. We photographed for over two hours and have, after rejecting a number showing only clouds, about ninety plates showing Venus on the sun. Telesoopically we are a success, photographically we are a partial one. The couimeneement and the close are al that can be observed through the telescope, while the middle is of the most importance in the photograph when the least distance between the centers o: the two bodiís can be measured, though these we have taken are very valuable Taking everything into account, we should be well satisfied, but we canno help wishing we had a been blessec with a clear day. We are now, as it were, undor ïnarching orders, and are expeotiug instructions as to whether we go by land or water to Shanghai,. Mhere we will most likely stay a little while and complete working up our observations, and theu uiake the best time for our homep.

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Subjects
Old News
Michigan Argus