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 XII. Proceedings of Learned. Societies. 



ROYAL SOCIETY. 



Abstracts of papers which have lately been read before the Royal 

 Society : — 



ON the elasticity of threads of glass, with some of the most useful- 

 applications of this property to various kinds of Torsion Ba- 

 lances." By William Ritchie, Esq., F.R.S., &c. 



The author proposes the employment of threads of glass in the 

 construction of torsion balances, in place of the silver wire used by 

 Coulomb, for the measurement of minute electric or magnetic forces. 

 He describes a galvanometer of his invention acting upon this princi- 

 ple, the intensity of the galvanic current being measured by the tor- 

 sion of a slender filament of glass, to the lower end of which a mag- 

 netized needle is fixed at right angles. He also applies the same 

 power to the improvement of the sensibility of the common balance 

 for weighing minute bodies, by affixing to the beam a long glass 

 thread horizontally in the axis of suspension, by the torsion of which, 

 when the balance has been brought nearly to a level, the more accu- 

 rate adjustments are to be effected. On the whole he considers that 

 glass, from its perfect elasticity, possesses decided advantages over 

 metallic wires, for the construction of instruments acting on the prin- 

 ciple of torsion. 



" On the quantities of water afforded by springs at various periods 

 of the year." By J. W. Henvvood, Esq., F.G.S. Communicated by the 

 President. 



It has been a matter of dispute, whether the whole of the water 

 afforded by such springs as are but little influenced by the change of 

 the seasons was derived from rain. With the hope of elucidating this 

 question, the author endeavours to ascertain the comparative quan- 

 tities of water yielded by the same spring at different periods ; and to 

 obtain simultaneous observations in springs rising in different strata 

 and existing at considerable depths in the earth. For this purpose 

 he has availed himself of the information contained in a paper by the 

 President of the Royal Society, of which an abstract was given in the 

 last number of the Phil. Mag. and Annals, on the performance of 

 steam-engines in the Cornish mines. The details of these investigations 

 occupy several tables. After making due allowance for the loss of 

 water, owing to imperfections in the engine, which he considers as 

 nearly balanced by the amount of rain-water which penetrates from 

 the surface and is carried off by the adit, he thinks himself warranted 

 in assuming the actual quantity of water raised by the engine, as re- 

 presenting with sufficient accuracy that which would be naturally 

 afforded by the springs of the mine. On comparing the known quantity 

 of rain falling in any district with the quantity of water given out by 

 its springs, added to that returned to the atmosphere by evaporation 

 from the same district, which he estimates according to Mr. Daniell's 

 method, he finds the former of these quantities is to the latter nearly 

 in the proportion of two to three. After adverting to the hypothesis 

 of the infiltration of sea- water, which might be proposed in explanation 



of 



