290 Mr. M. Donovan on the supposed Identity of the Agent 



It can only have arisen from a passion for verbal generalization, 

 whether the philosophy of the subject would admit of it or not. 

 Some parts of Mr. Potts' s discourses on the subject might be 

 amplified with advantage, and especially with respect both to 

 more numerous and more elaborate examples, and to the cha- 

 racter of analysis when applied to local and indeterminate pro- 

 positions. I am not altogether without the hope that these 

 changes will hereafter be made. 



XLII. On the supposed Identity of the Agent concerned in the 

 Phenomena of ordinary Electricity, Voltaic Electricity, Electro- 

 magnetism, Magneto-electricity, and Thermo-electricity. By 

 M. Donovan, Esq., M.R.I.A. 



[Continued from p. 213.] 

 Section III. 



IN furtherance of the objects described in the preceding sec- 

 tion, Professor Faraday has made experiments to determine 

 the cpiantity of electricity associated with the particles or atoms 

 of matter. He says it is wonderful to observe how small a 

 quantity of a compound body is decomposed by a certain portion 

 of electricity. One grain of water will require for decomposition 

 an electric current " equal to a very powerful flash of lightning*." 

 Elsewhere he says, "the chemical action of a grain of water upon 

 four grains of zinc can evolve electricity equal in quantity to that 

 of a powerful thunder-storm f." And he further declares, that 

 from his experiments "it would appear that 800,000 such 

 charges of the Leyden battery would be necessary to supply 

 electricity sufficient to decompose a single grain of waterj/^ 

 The Leyden battery to which he here alludes consists of fifteen 

 jars containing 3150 square inches, that is, about 24| square 

 feet of coated glass, charged by thirty turns of a plate electrical 

 machine* the plate being 50 inches in diameter, and of immense 

 power, giving ten to twelve sparks an inch long for each revo- 

 lution. 



The estimate that 800,000 discharges of the battery of fifteen 



by assuming that what is required to be done is done, and then by reason- 

 ing from the more complex to the more simple, finally arriving at a known 

 truth. Analysis is the method usually employed in algebra." 



Comment on this would be superfluous. Even the second sentence, 

 repeated as it has been parrot-like from D'Alembert's calling algebra " ana- 

 1;. is" down to our own time, is not more than partially true. It is usually 

 true as regards the solution of prohlems, but very rarely so in the investi- 

 gation of theorems. D'Alembert greatly confused our conceptions of 

 science by that unfortunate substitution. 



* Researches, par. 853. t Ibid. 8/3. J Ibid. 861. 



