260 Researches in the Theory and Calculus of Operations, 



duced gravity, to be followed by a second stratum, etc. (this 



is convection). 



The transition from the calorific to the luminific? form of 

 vibration will be achieved by supposing the intensity of 

 the collision to be so great as crush the spherical atomic 

 force into a flat circular plate, as in B, where the oscillations 

 will be perpendicular to the direction of propagation. 



When a ray from the Sun, or other luminous body, strikes 

 the surface of a terrestrial substance A (fig. 10), it excites 

 spherical vibration in the atomic forces of the substance; 

 and as a continued stream of these calorific atoms arrives 

 from the source, the concussed forces of the substance en- 

 large, and the substance increases in bulk, while at the same 

 time the accumulating atomic force reacts and increases the 

 thermometrical temperature of the surrounding medium. 

 As the concussion is very forcible, the successively striking 

 atoms are flattened against the surface of the substance, 

 and take the form of plane vibration in all directions 

 around the centre of the ray, exhibiting the phenomenon 

 of light. At the circumference of these plane circular oscil- 

 lations, the forces of the surrounding medium have yet 

 sufficient energy to effect certain chemical results, which 

 appear in the progress of vegetation, and subserve also the 

 photographer's art. In this order, then, are arranged the 

 calorific, the luminific and the actinic dimensions of the 

 solar spectrum. A circular prism ought to show a circular 

 spectrum around the centre of the impinging ray. 



A glance at the accompanying figure will show that lines 

 drawn from all points of the Sun or other luminous body 

 A (fig. 11), to the several points of the surface of the atomic 

 spherical force of which aca r is the diameter, encounter 

 radiating lines from this sphere audits centre in all possible * 

 directions, giving rise to multitudinous interferences of the 

 small tangent planes whose vibratory motions constitute 

 the phenomenon of light, and which interferences are neces- 



