Notices respecting New Books. 295 



In the use of this hygrometer, the person of the experimenter 

 can easily be kept at a sufficient distance from the condensing 

 surface; and in the ordinary mode of operating at an open win- 

 dow whilst the little brass bottle is in the open air, the body of 

 the experimenter is of course in the room. AVere it thought 

 necessary, a small telescope or opera-glass might be used to 

 observe the surface, whilst the handle of the piston-rod might 

 be lengthened so as to admit of still greater distance. 



XXXVII. Notices respecting New Books. 



Experimental Researches in Electricity. By Michael Faraday, 

 D.C.L., F.R.S. <Sc. SiC. 3 vols, 8vo. London: Taylor and 

 Francis. 



I^HREE volumes of Faraday's Experimental Researches are now 

 before the public. They embrace his contributions to the 

 Philosophical Transactions, the Philosophical Magazine, and other 

 journals during a period of upwards of thirty years. The first of these 

 volumes opens with the celebrated memoir on Voltaic and Magneto- 

 electric Induction. In the year 1820 Arago and Humboldt were 

 making experiments on terrestrial magnetism on the slope of Green- 

 wich Hill : Arago observed that the magnetic needle came more 

 quickly to a state of rest when in proximity with certain bodies, 

 and following up this observation he founded upon it his so-called 

 magnetism of rotation. The investigation of the force which pro- 

 duced the rotation of the magnetic needle occupied for years the 

 attention of English and continental philosophers ; exact experi- 

 ments were made and explanations given, all of which, however, 

 were overthrown by the subsequent experiments of Arago himself. 

 The fact stood forth as a challenge to the natural philosophers of 

 the day, until in the year 1831 Faraday crushed the difficulty, and 

 embraced the discovery of Arago in that of magneto-electric induc- 

 tion — a discovery which rivals in importance that of the pile by 

 Volta, and, indeed, already threatens to supersede the latter in its 

 most important practical applications. 



There are men, who, having made a great discovery — having passed 

 the trying furnace of thought through which such a result is ap- 

 proached, — rest contented with their achievement, and evince no 

 desire to renev/ the struggle by which their laurels were won. The 

 great Italian whose name we have mentioned, suffers in this respect 

 by a comparison with Faraday. The latter drew from his dis- 

 covery courage and strength to go on to others, and the volumes 

 now before us are the practical record of a life of scientific activity 

 unexampled in result since the time of Newton. Faraday has 

 not been disciplined in the accredited schools of science : he 

 has figured the operations of nature in his own fashion before his 

 mental eye, and the very richness of his imagination in tliis respect 

 often places his readers in difficulty. We question much whether 



