48$ 



Messrs. T. and A. Gray and J. J. Dobbie. [Apr. 24, 



April 24, 1884. 



THE PRESIDENT in the Chain 



The Presents received were laid on the table, and thanks ordered 

 for them. 



Professor Leopold Kronecker, Foreign Member, was admitted into 

 the Society. 



The following Papers were read : — 



I. " On the Relation between the Electrical Qualities and the 

 Chemical Composition of Glass and Allied Substances." 

 Part I. By Thomas Gray, B.Sc, F.R.S.E., and Andrew 

 Gray, M.A., F.R.S.E., Assistant to the Professor of Natural 

 Philosophy in the University of Glasgow, and J. J. Dobbie, 

 M.A., D.Sc. (Edin.), Assistant to the Professor of Chemistry 

 in the University of Glasgow. Communicated by Pro- 

 fessor Sir William Thomson, F.R.S. Received March 29, 

 1884. 



The relation between the composition of glass and its electrical 

 qualities has been studied by only a few experimenters, and our 

 knowledge of the subject is still comparatively small. With regard 

 to resistance to electrical conduction through its substance, Dr. 

 Hopkinson has found among other interesting results, that potash or 

 soda-lime glasses have a higher conductivity than flint glasses either 

 light or dense ; and his results as to electrical resistance confirm 

 those given below.* 



That the presence of a large quantity of alkali in glass is 

 detrimental to its resisting quality has also been pointed out by 

 Ekman.f In two papers (" Phil. Mag.," vol. 10, 1880, and " Proc. 

 Roy. Soc," vol. 34, p. 199), by one of the authors of the present 

 paper, results are given of experiments on the variation of the 

 resistance of glass of different kinds with temperature, and, more 

 particularly in the second paper, with density and chemical composi- 

 tion. 



It was inferred from the results of the electrical measurements 



* " Phil. Trans.," vol. 167. 

 f " Phil. Mag.," vol. 40, 1870. 



