Correspondence.

Evening Star, Issue 3708, 11 January 1875, Page 3

Correspondence.

We are not responsible for the opinion) expressed by oar correspondents.]

To the Editor. Sir, —Professor Peters is reported to have said at the dinner given by the Otago Institute to the members of the French and American Transit of Yenus expeditions that “ the angle which they had to ascertain was equal to an angle formed by a hair extended at a distance of 8,000 feet.” They had to mepsnre the thickness of a human hair at a distance of 8,000 feet.” May I ask, through you, Sir, in which work of Sir John Herschel’s (the authority given by Professor Peters) information respecting this very interesting subject is to be obtained ? Dunkin, of the Royal Observatory, and Lockyer, of the Durham University, have both stated that the difference between the parallax deduced from Transit observations in 1769 and that which is now supposed to be the corn et parrallax amounts to a little more than threetenths of a second, “which is equal to an angle subtended by a human hair at a distance of 125 feet.” If the angle sought ir the Sun’s true parallax, supposed to be about B.9secs., the distance at which an angle equal to this will be subtended by a human hair will amount to only a fraction of 125 ft,, instead of 8,0 JOft, if the calculations of the authorities quoted are to be relied on. 1 f the writer of “ Rough A stronomical Notes ” will kindly give some little information on this subject, he will oblige many of your readers.

I have not the honor of Professor Peters’s acquaintance, or I would have sought information from that gentleman himself, and thus have incurred a debt of gratitude equal to, if not greater than that professedly entertained hy the President of the Otago Institute towards Lieutenant Bass, for having been the means of forming him into “ an integral part” of the transit of “the fickle goddeßa,” —I am, &c., ' Ikq'UTPEH.