66 RAYS DEEMED IMPONDERABLE. 



the order in which the rays stand, corresponds with that 

 of their inflexibility and deflexibility, the red possessing the 

 most, and the violet the least. 



This was suspected by David Rittenbourg, but first demon- 

 strated by the ingenious experiments of Mr. Brougham. 

 Light, when passing obliquely from one medium to that of 

 another of greater density, assumes a direction different from 

 its original line, it is then said to be refracted, and bends 

 towards the perpendicular; and if that medium is a com- 

 bustible body, the refraction is proportionally greater, as its 

 attraction for light is greater than that of an incombustible. 



The refracting power of water induced Newton, who was 

 acquainted with this law, to suspect that it contained some- 

 thing of an inflammatory description in its composition, which 

 the subsequent analysis of water has fully authenticated. 



The red ray communicates to bodies the most powerful 

 degree of heat within the spectrum ; but it has been dis- 

 covered that there are invisible rays just without the red ray, 

 which exceed it in calorific powers, as stated by Dr. Wollaston 

 and Sir John Herschel. 



" The greatest illuminating powers are in nearly the centre 

 of the spectrum, the lightest green and deepest yellow." 

 HERSCHEL. 



Is this occasioned by the difference or excess of density, or 

 comparative specific gravity of the rays original and com- 

 bined, which occupy that portion ? 



It is not within our reach to ascertain in their highly 

 rarefied state, the proportional specific gravities of the rays 

 of light ; they have therefore hitherto been deemed, and are 

 called, imponderable ; but this arises from the insufficiency of 

 our means to designate the weight of what requires the most 

 minute and delicate application, and to such as we never can 

 in reason aspire. But as light is admitted to be a substance, 

 occupying space, subservient to the laws of attraction, and the 



