268 Proceedings of the Royal Society. 



act after the rotation has ceased, but were greater in intensity, 

 and that the former effects were such as might have been looked 

 lor from a knowledge of the latter* 



May 19. — George Harvey, Esq., John Smirnove, Esq., and 

 the Rev, Dr. Morrison, were admitted Fellows of the Society. 



A paper, entitled Some Accomit of the Transit Instrument lately 

 put up at Cambridge Observatory y by Robert Woodhouse, Esq., 

 F.R.S., was communicated by the author. 



The author in this paper first described the operations by which 

 the New Transit Instrument, at the Observatory of Cambridge, 

 was approximately placed so as to allow of a meridian mark being 

 erected on the distant steeple of Granchester church. He then 

 entered into a more full consideration of the different methods pro- 

 .posed and employed by astronomers for executing the more deli- 

 cate adjustments of the Transit in general — he shewed how the 

 errors of coUimation, level, azimuth, and the clock, may all be 

 detected, and their values determined by the resolution of certain 

 equations of the first degree, constructed from observations of 

 any three or more stars ; but this method, though exact in theory, 

 he reprobated in practice, and prefers making each adjustment 

 separately, and by the ordinary mechanical trials, as shorter, 

 more effectual, and less troublesome. Mr. Woodhouse then de- 

 scribed a remarkable phenomenon presented to him by the transit 

 in the course of his observations. He found that the line of col- 

 limation of the instrument deviated occasionally to the east or 

 west of the centre of the meridian mark without any apparent 

 reason. At length, however, it was found that this was caused 

 by the approach of the assistant's body to the lateral braces placed 

 for the purpose of steadying the instiniment in an invariable posi* 

 tion at right angles to its axis. The expansion of the brace 

 nearest to him was found to thrust the axis of the telescope 

 aside, and on the removal of the assistant, the equilibrium of tem- 

 perature restoring itself, the deviation gradually disappeared. That 

 4his was the true cause appeared by wrapping hot cloths round th^ 



