Chap. 4-] Eleftrkal Attraction* 29 



culiar fpecies of attraction will be more amply treated 

 of in a fucceeding part of the work. 



There is a property fuppofcd to be incidental to 

 matter, which is oppoiite to this of attraction 7 , and 

 which is therefore denominated REPULSION, It is a 

 maxim of the Newtonian philofbphy, that where the 

 iphere, or power of attraction, terminates, that of re- 

 pulfion begin*. In the inftance which has been already 

 adduced of the round drops of dew upon the leaves of 

 plants, it is fuppofed not only that there exifts an at- 

 tractive force between the particles of the fluid, but a 

 repulfive force between them and the leaf on which 

 they are fufpended. That the drops are not in actual 

 contact with the leaf is evident from their white or 

 pearly appearance ; for this appearance refults from 

 the copious reflection of white light from the flattened 

 part of the furface contiguous to the plant ; and it is 

 well known that this effect could not take place, un- 

 lels there was a real interval between the under furface 

 of the drop, and the contiguous furface of the plant *, 

 The fact is alfo evident from another circumftance; 

 the drop is not found to have the fmalleft adhefion to 

 the leaf, but rolls off in a compact body with the great- 

 eft eafe, which it could not do if the fluid was in actual 

 contact with the leaf; or if there fubfifted any degree 

 of attraction between them. 



In the' fame manner needles or other light metallic 

 bodies will fwim on the furface of a fluid. Flies walk 

 upon water, and oil obftinately refufes to mix with 

 that and other fluids. Hence the feathers of water 

 fowl, which are covered with a thin coating of fubtilc 

 oil, actually repel the lurrounding water. 



* Prieftley's Optics, p. 4;*. 



This 



