Royal Society, 14<1 



on the theory ofaccidental colours hedoes not seem to be aware 

 of the facts and discussions in this Journal, vol. xv. p. 441, 

 Dec. 1839. 



St. Leonard's College, St. Andrews, 

 July 10, 1844. 



XXII. Proceedings of Learned Societies, 



ROYAL SOCIETY. 

 [Continued from vol. xxiv. p. 468.] 

 May 16. A PAPER was read, entitled, " On the Measurement 

 -^^ of Distances by the Telescope." By Edmund Bow- 

 man, Esq., C.E. Communicated by S. Hunter Christie, Esq., Sec. 

 R.S. 



The method proposed by the author for determining distances by 

 means of a telescope, consists in placing, at the spot of which the 

 distance is required, a graduated staff, and observing the number of 

 its divisions comprehended in the field of the telescope, or included 

 between fixed points in a diaphragm placed in the focus of the eye- 

 glass. He finds that the number of these divisions, apparent in the 

 field of view, are directly as the distance of the staff", plus a certain 

 constant, which depends on the construction of the instrument. The 

 author investigates the value of this constant, and illustrates the prac- 

 tical applications of his method, which he thinks might be employed 

 with great advantage in surveying, when, from irregularities of 

 ground or difficulties of access, the direct measurement by the chain 

 would be inconvenient or impossible. 



2. " AnAccount of some Experiments exhibiting new instances of 

 the Absorbing Power of Streams ; with a few remarks on the Pul- 

 sation of Jets." By Mr. G. Robinson. Communicated by W. 

 Bowman, Esq., F.R.S. 



The experiments of which an account is given in this paper 

 illustrate the absorbing power of a stream of fluid, whether issuing 

 from the open orifice of a reservoir, or flowing through rigid tubes. 

 The effects of this power are seen in the position of the fluid con- 

 tained in a vertical tube open at both ends, placed within the reser- 

 voir, and of which one end is brought within the influence of the 

 effluent stream : and also, when one end of a bent tube is brought 

 into the stream issuing from the open orifice of a reservoir, while 

 the other end is immersed in a coloured fluid. The author accounts 

 for the intermitting or pulsatory character of the jet issuing from an 

 open horizontal pipe, having a small hole on the upper side, by the 

 introduction of air, which, accumulating from time to time, forms a 

 bubble, which when it has attained a certain size, occasions an 

 obstruction to the free passage of the liquid, until the obstacle is 

 overcome by increased pressure from behind, and the jet then re- 

 sumes its former velocity. These changes occurring periodically, 

 give rise to the appearance of pulsation which is observed in these 

 circumstances. 



May 23. — 1. " Meteorological Register kept at the Master At- 



