II 



reflection of the light from the flattened parts of its sur- 

 face, contiguous to the plant. When the drop rolls 

 along a part which has been wetted, it immediately loses 

 all its lustre. The green plant being then seen clearly 

 through it, whereas in the other case it is hardly to be 

 discerned. 



" From these two observations laid together, we may 

 conclude, the drop, when it has the lustre, does not 

 really touch the plant, but hangs in the air at some dis- 

 tance from it by the force of a repulsive power : for 

 there could not be so copious a reflection of light from 

 its under surface, unless there were a real interval be- 

 tween it and the surface of the plant. 



" Now if that surface were perfectly smooth, the under 

 surface of the drop would be so likewise, and would 

 therefore reflect the image of the illuminating body like 

 a piece of polished silver ; but as it is rough, the under 

 surface of the drop becomes rough likewise, and so re- 

 flecting the light copiously in different directions, as- 

 sumes the colour of unpolished silver*" 



Again : Rays passing from a more rare into a more 

 dense medium, are turned out of their right line, because 

 more strongly attracted by the denser medium. 



Rays of light differ in respect of refraction, reflection, 

 and colour. Those that agree in the first of these 

 agree in all, and may therefore be termed homogeneal r 

 colours exhibited by them \ve may call homogeneal 

 colours. This being premised, we may observe, 1. That 

 the sun's light consists of rays variously refrangible. 

 2. The rays variously refrangible, when separated from 

 each other, exhibit different colours. 3. That there are 

 as many simple, homogeneal colours, as there are de- 

 grees of refrangibility. 4. A composition of all the 

 simple colours is requisite to constitute whiteness. 

 5. The rays of light do not act upon one another in 

 passing through the same medium. 6. Neither do they 

 thereby suffer any refraction. 7. The sun's rays con* 

 tain all homogenous colours, which may therefore be 

 called primitive. 



B5 



