1826.3 Dr» Thomson* s Answer to Mr. Rainy, 359 



gas and three voli^>e§,,Qf ^4'^qgejqijig^s^,^90ud€nsed into two 



volumes. -o ,ji..)i!.fcOi'>ydiiur'=: *o PiS>riitf . 



2 volumes ammomacal gas weigh. . 1*180474 

 ,, , I Subtract 1 volume azotic gas .... 0*972222 



Remain for 3 volumes hydrogen gas 0*208252 



The third of which/ ot 0*069417, must represent the specific 

 gravity of hydrogen gas. 



Now 0*069417 : Mill :: 1 : 16*006. 



Thus we see that the specific gravity of hydrogen gas deduce^ 

 from that of ammoniacal gas is within -g-^L. th part of ^th of that 

 of oxygen gas. 



4. Water has been shown to be a compound of one volume of 

 hydrogen gas and half a volume of oxygen gas united together, 

 and condensed into a liquid. 



Weight of a volume of hydrogen gas 0*069417 



Weight of half a volume of oxygen gas .... 0*555555 



Now 0*069417 : 0*555555 :: 1 : 8*003 



Here we have the same ratio as before. 



The compositions of water and ammonia have been deter- 

 mined with fully as much care as any thing within the whole 

 range of chemical science ; and they concur in establishing the 

 ratio between the specific gravities of hydrogen and oxygen 

 gases to be 1 : 16. Indeed I am aware of very few numerical 

 ratios in any department of science that have been determined 

 with so much accuracy. 



5. Even the specific gravity of vapour, upon which Mr. Rainy 

 lays so much stress, and which he considers as so completely 

 established, leads to the same conclusion, or rather indeed is 

 founded on the assumption of the truth of this ratio. This spe- 

 cific gravity has been settled at 0*625. 



Now vapour is a compound of one volume of hydrogen gas 

 and half a volume of oxygen gas united together, and condensed 

 into one volume. If we subtract 0*555 from 0*625, the remainder 

 0*0694 must represent the specific gravity of hydrogen gas ; but 

 0*0694 : 1*1111 :: 1 : 16. 



Ill reality, therefore, all the calculations and objections of Mr. 

 Rainy were founded on the admission of the very ratio which he 

 endeavoured in his paper to overturn. 



I might easily brmg forward a great number of other proofs 

 that the specific gravity of hydrogen gas is exactly ^'-^-th of that 

 of oxygen gas. But I have' already extended this pa p^^ much 

 further than I originally intended j and I believe that in Great 

 Britain at least, the specific gravities of hydrogen and oxygen 

 gases, as I have here stated them, are universally '4dmitted to be 



