288 ANNUAL OF SCIENTIFIC DISCOVERY. 



by any of the instruments so often crossed by it. Professor Win- 

 lock, the astronomer at Cambridge, was informed of the discov- 

 ery, and after some search with the fine Munich telescope of that 

 observatory, detected the new star, although at first as elongated, 

 not double. The success of European instruments with the new- 

 test is yet to be heard from. The remarkable quality of Mr. 

 Campbell's telescope (a 12-inch lens, 3 inches smaller, if we mis- 

 take not, than that of the Munich instrument at Cambridge) is 

 due to the well-known skill of Mr. Clark, of Cambridgeport, who 

 has been engaged for months in correcting and perfecting it. 

 Scientific American. 



DISTANCE OF THE SUN. 



At the 1867 meeting of the " American Association for the Ad- 

 vancement of Science, 11 Prof. Newconib read a paper on a " New 

 Determination of the Distance of the Sun, 11 the calculations having 

 been made at the Washington Observatory. Ten years since astron- 

 omers began to suspect that the value of the sun's distance found by 

 Eucke from the transits of Venus observed in 1761 and 1769, was 

 largely in error. This distance, 95,300,000 miles, had long been re- 

 ceived as the standard. But all the modern tests which could be 

 applied to it indicated that it was about 3, 000, 000 of miles too great. 

 In the year 1862 circulars were issued independently from the 

 observatories of Washington and Pulkowa (the Russian national 

 observatory situated near St. Petersburg), inviting the co-opera- 

 tion of astronomers everywhere in a general attempt to determine 

 the parallax of Mars at apposition of that year. The plan was 

 generally adopted, and nearly every active observatory in the 

 world engaged in the observations, which occupied 10 weeks. It 

 was the most extended co-operate effort on the part of astrono- 

 mers which had been made during the century. 



It is now complete, and the sun's distance is determined to be 

 92,340,000 miles, and the velocity of light is thus reduced to 185,- 

 500 miles per second. 



THE TRANSIT OF VENUS. 



This important astronomical phenomenon, which is to take 

 place on the 8th of December, 1874, and again on the 6th of De- 

 cember, 1882, already begins to engage the thoughts of astrono- 

 mers, as those of the last century, which occurred on the 5th of 

 June, 1761, and on the 3d of June, 1769, engrossed the attention 

 of the past generation. The transit of Venus over the sun's disc 

 affords a direct observation of the planet's node, or point, where 

 its orbit cuts the ecliptic, an element which is of great value 

 for the correction of astronomical tables ; but it is chiefly impor- 

 tant for the determination of the sun's parallax (or angle) under 

 which an observer, situated in the centre of the sun, might see the 

 earth's radius. One side and two more elements of the six con- 

 stituting a triangle are requisite in order to determine the other 

 three ; hence, considering a right-angled triangle, having the ver- 

 tex of its right angle in the centre of the earth, one of the sides 



