fly Proceedings of Philosophical Societies, [July, 



any new or peculiar property of heat. The results show that 

 the fact is completely verified, and at the same time the peculiar 

 explanation rendered unnecessary ; as from observing the tem- 

 peratures acquired by the screens, it appeared that the effect 

 was exactly such as would be accounted for from the simple 

 circumstance of a secondary radiation from the screen. 



In the sequel of the paper the recent experiments of ^J^. 

 Ritchie were adverted to, who has maintained that simple heat 

 radiates directly through very thin glass when transparent, but 

 not when opaque. This result was tried by a different method 

 from Mr. R.'s, and no difference was found to be occasioned by 

 the transparency of such a screen. 



Thus two apparent exceptions to the general law "that 

 simple heat cannot permeate glass," are done away. 



An Account of a Telescope having only one Reflector, and of 

 easy Management in observing ; by the Rev. Abram Robertson, 

 DD. FRS. 



Account of some Experiments on the Laws of Electrical 

 Accumulations on coated Surfaces ; On the Construction and 

 Use of a Magnetic Balance ; and On the Electrical Conducting 

 Power of various Metallic Substances ; all by W. S. Harris, Esq. : 

 communicated by the President. 



June 8. — The Bakerian Lecture ; On the Relations of Electri- 

 cal and Chemical Changes; by Sir H. Davy, Bart. PRS. Was 

 read. 



The experimental investigations and results brought forward 

 in this Lecture, are prefaced by a historical sketch of the origin 

 and progress of electrochemical science, with a view of correct- 

 ing tne erroneous statements that have appeared on the subject. 

 The origin of this branch of knowledge is stated to be the dis- 

 covery of the decomposition of water by the voltaic pile, by 

 Messrs. Nicholson and Carlisle in 1800. This was followed by 

 the experiments of Cruickshank and of Dr. Henry, and by several 

 papers by the author himself, the chief contents of which are 

 stated, and in which the appearances of acids, and oxygen, 

 at the positive, and of alkalies, sulphur, and the metals, at the 

 negative pole, were described. 



The experiments of Hisinger and Berzelius, in 1804, are 

 placed next in order, which establish similar results; and in 

 1806, on the occasion of the agitation of the question respecting 

 the production of muriatic acid and fixed alkali from pure water, 

 the author presented to the Royal Society his Bakerian Lecture 

 on the Chemical Agencies of Electricity, in which he drew the 

 general conclusion that the combinations and decompositions by 

 electricity, were referrible to the law of electrical attractions 

 and repulsions — a theory in which, he observes, he has hitherto 

 found nothing to alter, and which, after a lapse of 20 years, has 

 continued, as it was in the beginning, the guide and foundation 



