Notices respecting Neio Books. 59 



formula is then explained, and its more important applications to 

 the various relations of electric forces and potentials stated in a 

 series of propositions. The general theory of electrical influence, 

 and the theory of condensers of various forms, cylindrical, spherical, 

 and plane, complete this chapter. The next chapter discusses the 

 distribution of electricity on two spheres in various relative posi- 

 tion, according to the calculations of Poisson, Plana, Thomson, &c, 

 and gives an account of Thomson's theory of electrical images. It 

 concludes with a comparison, at some length, of the phenomena of 

 statical electricity with those of thermal conductivity. Although 

 Poisson, Thomson, Clerk Maxwell, &c. have been largely drawn 

 upon in this portion of the work, the author is careful to refer to 

 those writers for details, and as a rule discusses mathematically 

 only those particular cases which admit of experimental verifi- 

 cation. 



We proceed to give a brief account of the other portions of the 

 work. The first chapter is preliminary ; the second, third, and 

 fourth give a very complete and admirable account of the experi- 

 mental researches of Coulomb and others on the laws of electric 

 action, the distribution of electricity on conductors of various 

 forms, its loss by the air and insulating supports, and the theory 

 of the proof-plane. The fifth chapter treats of the general pheno- 

 mena of electric induction, the behaviour of insulating bodies with 

 respect to the distribution of electricity in them, condensation, &c. 

 Chapter viii., on " Instruments of Measurement and Observation," 

 contains a classification of most of the types of electroscopes and 

 electrometers that have ever been used, and will be found useful 

 for reference. Though the descriptions are as a rule satisfactory, 

 there are some exceptions : e. g. the descriptions and pictures of 

 Kohlrausch's and Dellmann's electrometers are vague and inade- 

 quate ; an ordinary reader with these only for his guide will pro- 

 bably fail to understand the instruments. Lippmann's electro- 

 capillary electrometer is relegated to the last chapter. 



The tenth, eleventh, and twelfth chapters give an account of the 

 modes and effects of the electric discharge, mechanical, calorific, 

 luminous, &c, and also of induction produced by the discharge. 

 The researches of Verdet on this last subject are well described, 

 and also the more recently published researches of Bichat. Bichat 

 obtained powerful effects by passing the discharges of a Holtz 

 machine through the fine wire of an induction-coil, and collecting 

 the induced discharges manifested in the thick wire. Under these 

 conditions the difference in tension between the two induced dis- 

 charges was enormous, and the decomposition of water was effected 

 almost as completely as if a continuous current had been employed. 

 This decomposition M. Bichat shows to be due to the inverse 

 induced discharge. The thirteenth chapter is on " Electrical Ma- 

 chines." With respect to the Holtz machine, the author regards 

 as unnecessary the explanation of its action given by Biess by re- 

 ference to " double induction." He says, in order that double 

 induction may be produced, the insulated body must be electrified 



