Light, caloric, electricity and mahnetism 199 



finitively established by the pure reason, are certain for and by the prac- 

 tical reason, which without them would have no foundation. In other 

 words, morality cannot be demonstrated for the very reason that it is 

 absolute, and everything that it implies participates in its authority. 



IDENTITY OF LIGHT, CALORIC, ELECTRICITY AND MAGNETISM. 



These material agents have long been known to possess many points 

 of near approximation to each other in their various manifestations. As 

 the boundaries of our knowledge became more extended through scien- 

 tific investigation, each new discovery of their properties revealed to us 

 a nearer relationship between them, so that the opinion of the identity 

 of their cause or origin was very generally adopted by philosophers. 

 Of the truth of this opinion the recent discoveries of the distinguished 

 London Professor, Michael Faraday, have furnished us with the most 

 satisfactory evidence. 



It may not be unacceptable to our readers to have a brief account of 

 some of these discoveries, in connection with facts previously known 

 and belonging to our common stock of knowledge, spread out upon the 

 pages of the Record and Journal. 



1. Light and heat or caloric, though they obviously have many 

 points of difference, have so many of near relationship and resemblance 

 as, at once, to arrest the attention of every observer. 



Thus, when a body is heated, or according to the common view ca- 

 loric is accumulated within it, it becomes, at first, faintly, and, as the 

 temperature increases, at length brilliantly luminous. The increase of 

 the light evolved is in some degree proportionate to the temperature of 

 the body. At low temperatures it may be supposed light is given off, 

 but in quantities too small to make a sensible impression upon the or- 

 gans of vision, whilst at high temperatures the quantities are so great as 

 to make a powerful impression upon the eye. Here the one seems to he 

 converted into the other, or to bring it into activity. 



Again, in the solar ray, as well as in all cases of combustion, these 

 tioo agents always accompany each other. Every one knows that the 

 same means, as for example a lens or reflector, which is used to concen- 

 trate the one into a focus, is applied to accomplish the same object in 

 regard to the other. And this shows that they are governed by sub- 

 stantially the same laws. Both are capable of being reflected, transmit- 

 ted, refracted, and polarized under nearly the same circumstances. The 

 law of reflection is the same ; the good reflectors of light are in general 

 good reflectors of heat, tlic coincidence being only an approximation ; 



