::70 On the Tendenci) of 



phials contain the same elastic fluid in the 

 other, then no transmission is observable in 

 either : but if the retort, have common air, 

 or any other gas, v^ath out, and aqueous vapour, 

 or any other elastic fluid, except the outside 

 one, within ; then th^ motion in and out 

 commences, just as with the phials in similar 

 circumstances;.;, In fact this last ^observation 

 has since been verified by Dr. Priestley himself, 

 of which anliccount is given in No. 2, of the 

 American Philosophical Transactions, vol. 5. 

 After alluding itp his experiments above-men- 

 tioned he observ-es, " Since that time I have 

 " extended and diversified the experiments, 

 " and have ob^ryed^ thdt lyhat was done by 

 " air and w^l^r,. will be done by any two 

 [^ Jiljids ^ fl/r>i;and ;wbether tbey have afiinity 

 "'to one another ox not, that this takes place 

 "in circumstances, of which I, was not at all 

 " apprized before,, and such as experimenters 

 " ought to be^lac^uainted with, in order to 

 " prevent mistal>:es of considerable conse- 

 " quence.'' - 



The , facts stated above, taken altogether, 

 appear to me tojorm as decisive evidence for 

 that theory of elastic fluids whichT maintain, 

 and against the one commonly received, as 

 as any physical .principle .which, has ever been 

 deenied a. subject of dispute, can adduce. 



