1835.] BecquereVs Traitt Experimental, fyc. 145 



collect, from scattered sources, the numerous experiments which have 

 recently been performed so abundantly in elucidation of electricity, 

 and such a laudable enterprize deserves to be encouraged. To the 

 Englishman, this work cannot be perused without pleasure, because 

 he will find in it a view of the labours of his countrymen who are 

 taking the lead in this branch of Science, and who have essentially 

 contributed to increase to three large volumes what but a few years 

 ago was usually comprised in a few pages. 



The first book of the present volume of Becquerel's works is 

 devoted to the consideration of Electrical Statics ; the second book 

 treats of Magnetism, and the third of Electro-dynamics. 



1. There is an important question which it is a great object to 

 determine, in reference to the developement of electrity by friction. 

 Whether electrical phenomena derive their origin from the modifica- 

 tions which the ethereal substance supposed to surround the atoms of 

 matter undergoes, or from an imponderable fluid which exists in the 

 interstitial spaces of these atoms. Now, although the first be the 

 most probable of these suppositions, the facts hitherto observed are 

 insufficient to resolve the question. 



Another interesting subject of inquiry is the relation existing 

 between conductors and non-conductors of electricity, for all the 

 elements of bodies, when in solution, are provided with the property 

 of obeying the action of electrical forces. There are no data, how- 

 ever, by which this question can be determined. 



The author describes minutely electroscopes, or those instruments 

 which are necessary for detecting small quantities of free electricity 

 in bodies, and electrometers, a contrivance by which an approximation 

 can be reached of the charge of a machine, or of an electrical battery. 

 For appreciating the presence of feeble electrical currents, galvano- 

 meters, or multiplicators, are employed, in the adaptation of which, 

 M. Colladon has made some useful improvements. Under this head, 

 several tables of electrical intensities are given, which are of con- 

 siderable value. 



1. The influence of heat upon the disengagement of electricity 

 forms that part of the science which has been termed thermo-elec- 

 tricity. Cumming, Sturgeon, and others, have prosecuted the inves- 

 tigation of this subject with great vigour. It has been observed 

 that during the conduction of heat through a bar of metal the 

 electricity is decomposed, and united in a manner analogous to 

 the propagation of heat through bodies, and that, in a ring of 

 bismuth or antimony, if one half is cooled, whilst the other is 

 heated, an electrical current is instantly produced. Sturgeon has 

 observed some curious facts in reference to this point, but has not 

 been able to deduce any general conclusion from his experiments, 

 save that the developements of the currents in the masses of bismuth 

 and antimony of different forms, of which all the portions are not 

 endued with the same temperature, are to be attributed to the 

 crystalline arrangements which the atoms assume, for if a little tin is 

 added to these metals the thermo-electrical property is lost. Sturgeon 

 has observed that all metals possess analogous thermo-electric pro- 

 perties, provided the experiments be made on considerable masses. 



When the ring is constituted of different metals, or when a plate 

 vol. i. l 



