i 



cf Oil and Water. 43 7 



The a6Hon, however, of this great agent is 

 not fimple and uniform : it admits of great 

 variation, and operates by different laws, as 

 we fee in the different phenomena of gravi- 

 tation, ofcohefion, of electricity, of magnetifm, 

 and of chemical affinity. Thus, in our eledrical 

 and magnetical experiments, we have frequent 

 occafion to obferve, that the fame bodies which 

 are attradted by one are repelled by a third, 

 and inter fe, as the circumftances of the ex- 

 periment are varied. Perhaps, fomething of 

 the fame kind may limit or impede the at- 

 tradion of gravitation and cohefion, in particular 

 cafes. Hence philofophers have fuppofed another 

 principle of nature, oppofite to that of attraction, 

 v.'hich they have denominated repilfion^ and have 

 imagined the influence of this principle to begin, 

 where that of attraftion ends. The obfervations 

 deduced from the phenomena above alluded 

 to, have been transferred alfo to chemiftry ; 

 and becaufe certain bodies (liew no difpofition 

 to form a chemical union, they have been faid 

 to poffefs a repidfive faculty v/ith refpeCl to each 

 other. To fay, that a principle of repulfion 

 has no exiftence in nature, would be too pre- 

 fumptuous : but I am inclined to believe, that the 

 fpecies of attraction, which conflitutes chemical 

 affinity, is not counteracted by any principle 

 of repulfion in thofe cafes, where no affinity 

 appears to take place ; and that the apparent 



F f 3 repulfion 



