THE ELEMENTS Of COMMON AIR. 14^ 



a drop or two of ether into the vacuum of a common barome- 

 ter; it the temperature be 68**, the mercury will fall 15 inches 

 nearly; at the (ame time, if ether be admitted to a given bulk 

 of an_y kmd of gas, fubjedt to the preflure of the atmofphere, 

 the voliiiue will be doubled, clearly Ihewing that the elaftic 

 vapour from the ether is the fame in both cafes, namely, an 

 independent fluid of 15 inches force. 



I cannot iifmif"? this fubjeft without obferving, in juftice to Water does not 

 Dr. Thuii fun, that he has entered more clearly into my views <^'"o'veair. 

 of thefe fubjefts than any other of our own country who has 

 animadverted upon them. There are certain principles, how- 

 ever, which he, with moft chemifts of the prefent day, em- 

 braces, wiiich are, according to my experience, decidedly 

 erroneous. One of thefe is, that water dijfolves air. An ex- 

 cellent paper of Mr. W. Henry, on the abforption of gafes by 

 water, in the Philof. Tranfadions for 1803, has fhewn us fuf- 

 ficiently in what light we (hould view the fuppofed folution of 

 air in water. Certainly air that is retained in water by me- 

 chanical force, and which always efcapes when that force is 

 withdrawn, cannot with any propriety be faid to be held by 

 chemical affinity. 



Dr. Thomfon has been mifinformed refpefiing my opinions The author does 

 on the expanfion of liquids. In vol. i. page 343, he gives it "hj ef 'i^n'of 

 as my fuggeftion, that all liquids expand the fame quantity all liquids by 



from their freezing to their boiling temperatures. I never en- l'^'* " ^^^ ^*^^ 

 , ^ , " . . , . . . , ,, between conge- 



tertained luch an opmion ; and it is certamiy errpneous. My Jation and boil- 

 idea is, that pure and homogeneous liquids, fuch as water and '"S J but that 



^ , J- , /• r L any fingle fluid 



mercury, expand accordmg to the Iquare ot the temperatures expands accord- 



from the points at v;hich they congeal ; but I have not yet found '"g to the fquare 

 a law to regulate the relative expanfions of thefe and other "^^^ /ro^k"'* 

 liquids, freeaing point. 



I am your's, &c. 



J. DALTONo 



Manchefier, 

 June 1 6. 1 SO^. 



£«^ 



