1818.] Traitc de Physique exptrimentale et Mathematique. 61 



composed. Heavy bodies, for example, cannot be deprived of 

 their weight, nor their particles of the property of mutually 

 attracting each other. There are, however, other kinds of qua- 

 lities, which may be impressed upon bodies in a more transient 

 manner, and which are developed in them, without the addition, 

 so far as we can judge, of any tangible or ponderable principle. 

 In treating of electricity, the first of the qualities or modifica- 

 tions of the kind here referred to, the author first lays down its 

 general laws as they are ascertained by observation and experi- 

 ment ; then from these he deduces his theory, and afterwards 

 describes the various kinds of apparatus. The number of chap- 

 ters is 20, and they bear the following titles : general Phenomena 

 of electrical Attractions and Repulsions ; Distinction of the 

 two Kinds of Electricities ; of the Laws which the apparent 

 Attractions and Repulsions of electrified Bodies follow ; of the 

 Laws according to which Electricity is dissipated by the Contact 

 of Air and the Supporters which retain it imperfectly ; Disposi- 

 tion of Electricity in Equilibrio in insulated conducting Bodies ; 

 of combined Electricities, and of their Separation by Actions 

 without Contact ; Theory of the Motions excited in Bodies by 

 electrical Attractions and Repulsions ; of the best Construction 

 of electrical Machines, and the Conductors which form Part of 

 them ; of Electroscopes ; of what are stiled Electricites dissi- 

 muies, under which are included the Condenser, the Electro- 

 phorus, the Leyden Jar, and electric Batteries ; of electric 

 Piles, and of the Phenomena which Crystals electrified by Heat 

 present ; Applications of Electricity ; mechanical Effects pro- 

 duced by the repulsive Force of accumulated Electricities ; of 

 atmospheric Electricity, and Conductors for Lightning ; of elec- 

 tric Light; of the Development of Electricity by simple Con- 

 tact ; Theory of the electromotive Apparatus, supposing its con- 

 ducting Power to be perfect ; chemical Effects of the electro- 

 motive Apparatus ; Theory of the electromotive Apparatus, con- 

 sidered with regard to its imperfect conducting Power ; Exami- 

 nation of the Changes which take place in the electromotive 

 Apparatus in consequence of its Re-action upon itself; Modifi- 

 cations which result from its electric State ; of secondary Piles ; 

 on the unequal Resistance which the two Electricities experience 

 in crossing different Bodies, when they are very feeble. 



Magnetism forms the subject of the fourth book. The fol- 

 lowing topics are discussed in it : general Phenomena of mag- 

 netic Attractions and Repulsions ; general Considerations upon 

 tht' Development of Magnetism in magnetic Bars, and their 

 Analogy with electric Piles; Determination and Measure of the 

 directing Forces exercised by the terrestrial Globe upon Magnets ; 

 upon the different Ways of magnetizing; general Distribution 

 Of Magnetism in Bars by the double Touch; Laws of magnetic 

 Attractions and Repulsions ; Research into the Intensity of free 

 Magnetism in every Point of a Needle saturated by Means of the 



