514 PROFESSOR CHALLIS, ON THE DETERMINATION OF THE LONGITUDE, &c. 



It may be remarked that the effect of the forms of the pivots follows the same law 

 in 1854 as in 1850, but is of larger amount. The difference may reasonably be ascribed 

 to the wear of the pivots in the interval. Upon the whole I consider the final result obtained 

 by taking the forms of the pivots into account, viz. 22',70 East Longitude, to be a trust- 

 worthy determination. 



J. CHALLIS. 

 Cambridge Observatory, 

 May 15, 1854. 



P. S. It may be remarked that the measures for the determination of the effects of 

 the forms of the pivots were taken in April 1854, whilst the observations for the Longitude 

 were made in May 1853. Some allowance is, therefore, required for the change of effect 

 in the interval. By calculations recently gone through, of which an account will be given 

 in the published Cambridge Observations, and by having regard to the time during which 

 the Illumination was West in that interval, I find that the corrections for the forms of 

 the pivots should be less by the mean quantity s ,056. The Longitude should therefore 

 be increased by this quantity, and the corrected result is 22 s ,697 + S ,056 = 22',753. 



The value 22%75 East is now adopted for the Longitude of the Cambridge 

 Observatory. 



J. CHALLIS. 



Cambridge Observatory, < 



Oct. 16, 1854. 



