232 Analyses of Books. [March 



directly, and as the squares of the respective distances inversely ; 

 hence the attractive force between two parallel plane circles being 

 found, the force between any other two similar planes will be given. 



3d. The attractive force between two unequal circular areas is no 

 greater than that between two similar areas each equal to the lesser. 



4th. The attractive force also of a mere ring and a circular area 

 on each other, is no greater than that between two similar rings. 



5lh. The force between a sphere and an opposed spherical segment 

 of the same curvature, is no greater than that of two similar segments, 

 each equal to the given segment. 



It has been much agitated whether electricity can pass through a 

 vacuum, but the fact is, that as it is impossible to produce such 

 absence of matter by artificial means, it seems unnecessary to dwell 

 upon it. 



The experiments of Harris go to prove that electrical divergence 

 is completely independent of atmospheric attraction, and is therefore 

 in accordance with the opinion with which he sets out, that electricity 

 is a subtle material agent, essentially involved in the constitution of 

 ordinary matter. The experiments, however, upon which such de- 

 ductions can be founded, it is obvious, must be conducted with the 

 greatest delicacy, and in such cases, absolute certainty is scarcely to 

 be looked for. 



The paper of Dr. Faraday constitutes the Eighth Series of his 

 researches in electricity, and consists of corrected and extended views 

 of the theory contained in his Fifth and Seventh Series. The whole 

 paper is pregnant with important matter. It has been objected to 

 Dr. Faraday's papers on electricity that they are difficult to under- 

 stand, in consequence of the new nomenclature which he has intro- 

 duced, and perhaps there is reason, in some instances, in similar com- 

 plaints, for surely, it is said, when plain English words can express 

 facts or opinions, it is improper to substitute technical expressions, 

 either in science or literature ; and a language which can muster, in 

 alphabetical array, seventy-five thousand words, does not stand in 

 need of unnecessary innovations. Such observations, however, do not 

 apply in the present instance ; because, the new terms are few, and 

 obviate much circumlocution. They may, however, be attended to 

 with propriety by those who are only entering upon discovery. In 

 medicine, more especially, it is too obvious that technicalities have 

 served, in many instances, to form cloaks for ignorance and quackery. 



In the present series, the author enters upon the investigation of 

 the important point whether the supply of electricity is due to 

 metallic contact or chemical action. For the purpose of determining 

 this point, he took a plate of zinc, about eight inches long and half 

 an inch wide, which was cleaned and bent in the middle to a right 

 angle. A plate of platinum, about three inches long and half an 

 inch wide, was fastened to a platinum wire, and the latter bent to 

 a right angle. These two pieces of metal were arranged together, 

 but outside a vessel, and its contents, which consisted of dilute 

 sulphuric acid, mingled with a little nitric acid. A piece of folded 

 bibulous paper, moistened in a solution of iodide of potassium, was 



