53 



Astronomical Science s 



[July 



known (their distance in fact), we can determine the angle under which 

 the whole diameter of the Earth appears, when viewed from the Sun, 

 and hence the distance. 



The results of 1832 and 1834 give the angle, under which the equato- 

 rial diameter of the earth appears, when viewed from the sun, an d at her 

 mean distance, = 9", 253, which gives the mean distance = 88,319,500 

 miles. 



The comparison of the observed places of the sun and moon and 

 planets, with their places predicted in the Nautical Almanac, shews 

 that, with the exception of the four small planets, Juno, Ceres, Pallas 

 and Vesta, the places from observation are scarcely more accurate 

 than the predicted places. 



The next result arrived at, is one of some importance, namely, 

 the position of the equinoctial point. It need hardly be remarked, that 

 the equinoctial point being the zero, from which we measure the 

 right ascension and longitude of the heavenly bodies, any error, 

 in assuming its position, will affect, by the whole amount, the deter- 

 mination of every place (whether it be of a fixed star or planet) which 

 we observe. The late Dr. Maskelyne, the Astronomer Royal at Green- 

 wich, determined the true position of the equinoctial point with con- 

 siderable care, in the years 1790-1800 ; and in the years 1811-1820 

 the late Astronomer Royal (Mr. Pond) stated that the point thus de- 

 termined was in error, to the amount— 0,31" of time. Since this time, 

 other observations have been made thus— 



Error of Eq. Point 

 deduced by Maskelyne 

 From Greenwich observations in 1 81 1 — 1820 — 0,31 



— 1820—1827 — 0,21 



— Madras — 1832-1835 — 0,11 



Here we find a progressive change in the place of the equinox, differ* 

 ent from that which, according to theory, ought to obtain ; for, the 

 values above formed should (if Maskelyne's observations be correct) 

 be all=0. The discordance at the first date is too large to arise from 

 any probable error of observation, and the progressive change (which 

 follows the order of the date) is, to all appearance, due to some cause, 

 and not to accidental error of observation. 



Should future observations prove this position to be true, the dis- 

 covery will be an exceedingly interesting and curious one ; but, from 

 the minute amount of the variation, many years must elapse, before any 

 thing like a proof of its existence, will be obtained from observation, or 

 its cause accounted for by theory. 



The further results furnished from the Madras observations are the 

 longitude and latitude of the Observatory, thus : 



} } h. m. s. 



Longitude f of the 0bservatory f 5 21 8 E. of Greenwich. 



Latitude ) J 13 4 8,5 N. 



