12 On the apparent Changes 



tions, aiid some other mode of accounting for the phsenomena 

 must be resorted to. 



The atmosphere is a transparent continuous body : nor will 

 the division into ideal laminse, by imagining surfaces, produce 

 effects which depend upon a distinct separation of parts, into 

 distinct surfaces, severally belonging to the several media at 

 their confines. Of transparent continuous bodies, the reflec- 

 tions and refractions are only made at their confines, where 

 they are adjacent to other transparent continuous bodies of 

 different refractive powers, at which confines exists that state 

 of discontinuity and distance, upon which their reflections and 

 refractions depend. 



The difference of refractive powers of any two adjacent por- 

 tions of the atmosphere, if any difference can be supposed, if 

 any formation of laminae can be admitted, if any state, similar 

 to that of the confines of two different media of different re- 

 fractive powers, can be imagined to exist, at every mental or 

 ideal division of the continuous fluid of air — the difference, 

 it may be observed, of the refractive powers of tiiese portions 

 of the air where they join, cannot but be less than that of 

 crown glass and flint glass. The solid bodies of crown glass 

 and flint glass, pressed together by powers considerably less 

 than the ordinary weights of the atmosphere, may be made so 

 closely to approach together, that all reflection and refraction 

 will be extinguished at their confines, and light pass through 

 both, as uninterruptedly as through one continuous body. The 

 parts of the air are of one continuous body, and if they were 

 not, are yet so powerfully pressed together that they would be, 

 for the passage of light, as parts of one continuous body. 



When a portion of light, in a continuous transparent medium, 

 passes by the side or edge of any other body in that medium, 

 it is inflected or bent towards that body, in angles proportioned 

 to the distances of the parts of the light from the side or edge. 

 These bendings have been observed by philosophers, and by 

 them named inflections. The principal phssnomena of inflec- 

 tions^ more than thirty years ago, I observed and explained. 



