[ MO ] 



ceffary that it fliould be conceived to be sbrolutely Jimpk. We 

 know, for inftance, that atmofpheric air is a combination of at 

 leaft two diftind fluids ; and yet explain the phsenomena of the 

 barometer, air-pump, and condenfer, as depending merely on 

 its prefence or abfence, without any reference to the compofition 

 of its nature. In the fame manner fome eleftric phasnomena may 

 be juftly explained by confidering them as the effeds of the diffe- 

 rent diflribution of the fame fluid ; whilft its phofphoric fmell, its 

 power of changing blue vegetable colours to red, and its combuftion 

 may pofTibly be derived from its decompofition. 



