of the Heavenly Bodies, 23 



Let S, be the place of a spectator, ED the sun, LM a line 

 drawn through the centre of the sun parallel to the horizon, 

 TS a line drawn from the centre of the sun to the spectator, 

 HI a circular series of particles of vapour arranged at given 

 distances from each other in the same plane with LM, and TS, 

 and cutting TS at right angles, a ray of light from T passing 

 along TS, through the circular series HI, at right angles and at 

 equal distances between any two particles will proceed directly 

 without bending to the eye of the spectator. Let LH and MI 

 from the points L, and M in the line LTM, be rays parallel to 

 and in the same plane with TS. As TS falls perpendicularly 

 on HI, so LH and MI will fall obliquely on HI, and instead 

 of passing on to N, and C will be bent at H and I, 

 towards the perpendiculars to HI, into lines intersecting the 

 line TS, and coming to the eye of the spectator in the di- 

 rections SH, SI. This is the case with a single series of par- 

 ticles. Let the body of the sun ED be seen through many 

 strata consisting of many similar circular series of particles, 

 increasing in number and density in the several strata to the 

 surface downwards, a ray of light TS, entering between the 

 strata at right angles thereto, and descending through the 

 lower strata interposed between the luminary and the eye, will 

 be successively bent in the plane of the vertical in which TS is, 

 and a change and elevation of place of the point T in the vertical 

 will be produced. In this manner the points D and E, will be 

 raised to G and F, and all the points between D and E, to 

 places between G and F. But as in passing down between 

 various successive strata, other the rays LH and MI are acted 

 upon by two forces, one between the strata for elevating them 

 vertically, the other by the circular series they enter obliquely 

 for inflecting them towards their perpendiculars, these rays will 

 consequently move in directions diagonal to the directions of 

 these combined forces, and the points L and M will be not only 

 elevated, but dilated externally from and out of the vertical on 

 both sides, and apparently transferred to the points A and B. 

 In the same manner all the rays proceeding from all the inter- 

 mediate points of LEMD are variously elevated, dilated, and 



