ELEMENTARY PROPERTIES 



to anybody, or their abstraction, would make 

 no difference of weight capable of being detect- 

 ed by the most sensible balance ; eery attempt 

 then to ascertain the accumulation of light in 

 todies, by changes in their weight, must be hope- 



It is owing to this extreme state of exility, 

 connected with the inherent power of moving, 

 which the solar rays possess, that they are 

 enabled to penetrate the internal fabric of 

 bodies in general, whether diaphonous or opake. 

 This penetrating power is proved to be possess- 

 ed by them, from the impressions which they 

 excite on our organs of vision ; such is the com- 

 pact nature of the comm, or external coat of 

 the eye, that without this subtilty, the solar 

 ray, instead of penetrating it, would be arrested 

 by it, as well as by the other parts of which the 

 internal fabric of the eye is composed, and 

 never arrive at the membrane on which the 

 retina is spread, in which the impression is 

 deposited, and illumination produced. This 

 penetrating power is equally proved, by the 

 illumination which we, in consequence, enjoy 

 from it, through the medium of different bodies, 

 and more especially of our windows, insomuch 

 that glass (which is supposed from its inelasticity 

 to have its particles most intimately combined 

 -and compacted) of the most solid quality, 

 to its passage, neither impediment nor 



