Memoirs of the National Academy of Sciences Volume 2 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1884 edition. Excerpt: ...on six nights, but, owing to difficulty with the micrometer thread, two of these nights were not satisfactory, and observations on one or two of the others were much interrupted by clouds. It was found that on account of the nature of the climate several spider threads, although tight when put in, became quite slack soon afterwards. The atmosphere was very moist at night, and during the day the heat was excessive in the transit tent. After trying with unsatisfactory results several spider threads brought along with us, and two parallel fine copper wires, which were unsatisfactory for other reasons, it was thought that perhaps a spider thread found on the island would be less affected by climatic influences than those previously tried. Accordingly one was found and put in. It was rather coarse, very strong, and capable of being stretched tightly, and this one lasted during all the remaining observations. M. Palisa, of the European Expedition, gave up his diaphragm of spider lines and substituted a glass one in its place. The resulting value of the latitude deduced from four nights observations and 16 pairs is 10 00' 1."6. This value may be changed slightly by the final reduction of all the pairs with somewhat improved star places. The following is a specimen of the reduction of 1 pair observed on four nights: United States Coast /Surrey. Latitude Computation. Latitude station: Caroline Island. Instrument: Transit telescope No. 2, with latitude level. No. Declination. Corrections. Sum and half sum. Latitude. April 29.., 209 J 277 May 4t...... May7t-..L May8t....j.. Mean. Microm. Level. +14 18 0.90--19 46 35.25 Refr.-34 4 42.15 7.70 42. 58 8.30 42. 79 8.51 42. 86 9 53 17.62--0 44.08 34.88 17.44--0 41.71 34.49 17.25--0 40.62 34. 35...