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Mr. Ainger on the 



continues as far as the last rays tangent to the globule. Now if these 

 rays are received at such a distance from the globule, that this last may 

 be considered as a point, it is clear that all those which belong to unequal 

 deviations will diverge one from the other, as their distance from the 

 globule increases ; so that they will become too feeble to give a percep- 

 tion of the globule to an eye placed in their course ; while that eye would 

 be affected even at the same distance by the emergent rays, which cor- 

 respond to the maximum of deviation, because, being parallel, they are 

 transmitted to any distance without separation. 



' Suppose a series of these globules disposed circularly in such manner 

 that the refracted rays which issue from them, and which are supposed 

 to be of the same colour, may thus reach the eye ; they will produce the 

 sensation of a luminous line ; and several such series placed side by side 

 will produce a coloured band. 



' The same considerations apply equally to the cases in which the 

 refractions and reflexions are more numerous ; there is always for each a 

 limit at which the rays of a small pencil will emerge sensibly parallel, and 

 will be transmitted without becoming enfeebled. 



* To develop the consequences of these results, suppose that an 

 observer placed at (Fig. 4) views a large cloud composed of spherical 



drops of water ; draw from the centre of the sun through the eye the line 

 S O C, to designate the direction of the rays, which we will for the present 

 suppose to be exactly parallel; as would be the case if the sun were a 



