274 Historical Sketch of Electro-magnetism [Oct. 



causes, therefore, the temperature of ebullition is owing, 

 one corpuscular decomposition, which in the same fluid would 

 of itself always produce an ebullition at the same tempera- 

 ture ; and the other, the force of compression. The lique- 

 faction of solids, however, is controlled by one cause only ; 

 namely, corpuscular decomposition. Pressure, in this instance, 

 can have little or no influence ; for as pressure cannot increase 

 or diminish the individual intensity of collision, which is exclu- 

 sively due to the temperature, and can besides have no effect on 

 the facility of decomposition, which is in this instance likewise 

 exclusively due to the temperature and adaptation of the parts ;. 

 nor, moreover, on the state of the fluid product, which could 

 never be changed by mere steady pressure* whatever little 

 influence it may have on the volume, we cannot, therefore, infer, 

 that any sensible difference would be produced by external pres- 

 sure alone, however great it may be, in the temperature of the 

 liquefaction of solids. This inference, which agrees with the 

 experiments of our ablest philosophers, is another beautiful 

 instance of the accordance of phamomena with legitimate deduc- 

 tions from our general theory of the universe ; and, I believe, our 

 attempts to draw it are the first that have been made to unravel 

 the causes of a phenomenon, which becomes the more singular 

 and difficult when contrasted with its vacillating collateral-^ 



ebullition 



(To be continued.) 



Article IV. 



Historical Sketch of Electro-magnet ism. (With a Plate.) 

 (Continued from p. 200.) 



The results obtained by M. Oersted were immediately repeated 

 and confirmed by a great number of philosophers in various 

 places. Of these no one was more active than M. Ampere in 

 varying experiments, making new ones, and applying theory to 

 them. That philosopher read a paper to ' the Academy of 

 Sciences at Paris on Sept.. 18, in which he proposed a theory 

 that reduced all the magnetic phenomena to effects purely elec- 

 trical, and in many subsequent writings advanced further argu- 

 ments, both experimental and theoretical, in support of it. I am 

 desirous, however, at present, rather to mention the facts as they 

 were discovered than the theories attached to them: in the first 

 place, because they are of the most importance ; and in the 

 second, because there is no danger of attributing the theories to 

 any but those from whom they originate 



The facts discovered by M. Ampere, though nut numerous, 



