328 A Dijfertaiion, Isfc. , 



I am aware, that fuch calculations, in their own na- 

 ture, do not admit of that certainty which is demanded 

 in demonftratiouo Still they are fuiEciently accurate 

 to leave the mind fatisfied. I a^l alfo aware, that their 

 want of certainty comes with an ill grace from the 

 mouth of the objedor. As the advocates of the theory 

 prove, in the outfet, that many fprings are wholly fup- 

 plied in this manner ; the cafe with refped to the others, 

 is prima fade with them. As the objedor takes the if- 

 fue. the burden of proof refts upon his flioulders. Un- 

 til it is adually furniftied I believe we fhall all admit, 

 that Springs owe their origin only to Vapour. 



