348 



PROCEEDINGS OP THE AMERICAN ACADEMY 



P. E. 1 value -tO».0107 



P. E. 1 value ^0^.01 54 



So fiir as these observations go, there is no personal difference 

 indicated with certainty between B. and S. I am, however, inclined 

 to think tliat there may be a trifling one of the same order as that 

 apparent ; namely, S. — B. = -|-0^00y (witli a i)robable error of 

 ±0'.OOGU however); but I have not been able absolutely to prove 

 its existence. 



A somewhat plausible hypothesis, not usually adopted, is that for 

 hi(h northern declinations the ordinary probable error, due somewhat 

 to the rapidity of the motion of equatorial stars, ceases to hold good. 

 This l)yi)Othesis is somewhat favored by the fact that Bessel's time 

 determinations with the Reichenbach circle differed from Struve's by 

 a larwe amount, — more than one second; and that the difference 

 between the right ascensions of Polaris and 8 Ursa; Minoris, as deter- 

 mined by these two distinguished astronomers, seems to be due mainly 

 to their clock corrections. In other words, they observed the polars 

 alike, equatorial stars in an unlike manner. 



On this theory M. Gonnessiat's clock corrections would be too small 

 relatively to the Jahrbuch standard observer (Wagner) by -)-0'.33; 

 relatively to mine, by -j-0'-39. After subtracting these numbers the 

 remaining probable errors of one star, reduced to the eipiator, would 

 be ±0".013 and ±0'.U06 respectively. The first number, however, 

 would be reduced to a less quantity if the right ascension of Draco- 

 iiis 1 II. given in B. were corrected by the amount 



-j-OMGG +0'.0097 (X — 1875), 



which I have elsewhere indicated as probable ; this value has been 

 since very nearly confirmed by Pulcova observations for 1875.0 and 

 1880.0, which I owe to Vice-Director Wagner's kindness. 

 These values are, — 



