; 2(74 ON MIXED OASES. 



-Obfervations on m«fpheric fOTCC ; it QUght to be juft -J by the table above 



i^tte^n mixed ^^^^^^^ ^^' ^^^ »t is obvious, that by removing the hand 



gafes. occafionally, the full quantity of vapour for any temperature 



could never be obtained in this way, no more than pure oxigen 



.could be procured in the botlle by a fimilar procefs. The 



.grand queftion with Mr. G. however, is. How does vapour 



of half an inch force, expand the pores of air fubjedl to 30 



inches of preflure ? And his anfwer feems to be, it is impoffible, 



according to the axioms of dynamics. This queflion is what 



.1 (hall now confider. 



Having myfelf iludied the principles of dynamics, as well 

 as thofe of many other mathematical and phjfical fciences, 

 under the tuition of Mr. Gough, I feel under ftrong obliga- 

 - lion to him ; but thefe, he will readily grant, do not bind 

 me to fubfcribe to his opinions, when I cannot, perceive them 

 to be well founded. He charges me, in the prefent inftance, 

 with a miflake in regard to dynamics ; but he has not pointed 

 out any particular axiom which! have offended : The miftake, 

 I think, is with him, and fliall endeavour, in what follows, 

 to point it out. 



It is a principle in dynamics, that whenever a fyftem of 

 bodies ad upon each other, and are in a fiate of equilibrium, 

 the leajl farce rmprefled upon any one difturbs the equilibrium. 

 Thus, the ocean and the air, though bound to the earth by- 

 its fuperior attradion, are neverlhelefs difturbed by the feebler 

 influence of the moon. Air in a bottle is a fyftem of particles 

 at equal difiances repelling each other, but in equilibrium by 

 the gravity of the incumbent atmofphere ; confequently the 

 kaji force imprefled upon them rauft difturb that equilibrium. 

 Now, ex hypothefi, air does not repel vapour at a diflance, 

 but only in conta6t ; therefore vapour can be formed in fuch 

 a fyftem : when once formed, it meets with no elaflic refift- 

 ance or repulfion but from particles of its own kind ; there- 

 fore it is conflantly tending outwards, where the particles of 

 its own kind are leaft denfe : in its way it infringes upon par- 

 ticles of air, and exerts fuch force as it is capable of upon 

 them : a number of particles of air are thus gently propelled 

 in the diredion of the ftream, and the refl of the fyllem are 

 obliged to accommodate themfelves in order to preferve ibe 

 equilibrium : thus the diftaaces of the particles of air are gra- 

 4 duall/ 



