350 



from the remote end of the church, heard the voice in a direction the 

 reverse of that from which it really proceeded. 



The superior distinctness of sounds proceeding from the focus is 

 accounted for by their all arriving at the same moment of time at a 

 plane perpendicular to the axis, after reflexion from the surface of the 

 paraboloid ; which is a consequence of the equality of the paths they 

 have described. 



On the mutual Action of Sulphuric Acid and Alcohol, and on the Na- 

 ture of the Process by which Ether is formed. By Henry Hennell, 

 Esq. Communicated by William Thomas Brande, Esq. F.R.S. 

 Read June 19, 1828. [Phil. Trans. 1828, p. 365.] 



The most abundant product resulting from the mutual action of 

 sulphuric acid and alcohol, without the application of heat, is the 

 sulphovinic acid ; but on distillation this peculiar product disappears, 

 and ether is formed ; and it becomes a question what part the sul- 

 phovinic acid plays in this process. In opposition to the assertion of 

 Messrs. Dumas and Boullay, that this acid is not concerned in the 

 production of ether, the author contends that whenever ether is 

 formed, it is in consequence of the decomposition of the sulphovinic 

 acid. He obtained ether from this latter fluid by distillation, when 

 neither sulphuric acid nor alcohol were present ; but if a certain 

 quantity of water has been previously added, the sulphovinic acid is 

 resolved into alcohol and sulphuric acid, and no ether is obtained ; 

 whereas during the distillation of ether in the ordinary way, the sul- 

 phovinic acid is re-converted, more or less, entirely into sulphuric 

 acid. Hence he infers that the formation of the sulphovinic acid is 

 a necessary and intermediate step to the production of ether from 

 alcohol and sulphuric acid. As ether may be formed from alcohol, 

 by the intermedium of sulphuric acid, so by the same intermedium 

 may alcohol be obtained from ether, the sulphovinic acid being in 

 either case formed according to the mode of combination of the hy- 

 drocarbonous base. This theory is also illustrated by the employ- 

 ment of olefiant gas as the hydrocarbonous base, for by combining 

 this gas with sulphuric acid, we may form sulphovinic acid, from 

 which we may obtain at pleasure, by varying the circumstances of 

 the decomposition, either alcohol or ether. 



Experiments and Observations on Electric Conduction. By William 

 Ritchie, A.M. F.R.S. Rector of Tain Academy. ReadJune 19, 1828. 

 [Phil. Trans. 1828.J9. 373.] 



According to the modern theory of electricity, metallic bodies, far 

 from attracting the electric fluid, as is commonly believed, are of all 

 bodies those which have the least attraction for that fluid, and being 

 the best conductors for it, are entirely passive during its transit 

 through them. In confirmation of these views, the author describes 



