358 Mr. Moyle's Analysis of the Atmosphere 



measure not less than one gallon each : it is desirable that the 

 ends should be at least fifteen fathoms from any shaft or 

 winse, not more than twenty fathoms above the deepest level 

 of the mine, nor less than 100 fathoms below the adit, &c.," 

 through the Royal Cornwall Polytechnic Society, and that 

 premium having been awarded to the author of this com- 

 munication, he has considered that an abridged extract from 

 the essays published by that Society in their Transactions 

 for 1839 and 1840, may be acceptable to the readers of the 

 Philosophical Magazine. 



The analysis of gases, and more especially their combina- 

 tion or mixture in atmospheric air, being attended with no 

 small difficulty of manipulation, (nor are the precautions re- 

 quisite for obtaining accurate results of no mean consequence) 

 it may be desirable to premise with a few observations on the 

 different points of consideration so necessary for this purpose, 

 and which are fully detailed in the essays themselves. 



A due correction was made in all the following experi- 

 ments, with the utmost care, for any change of temperature 

 during the progress of the individual experiment. 



The necessary allowance for the presence of vapour in the 

 gas was always made according to Dr. Dalton's table. The 

 unaccountable tendency or propensity which gases possess to 

 unite, by overcoming obstacles placed for their security or 

 separation, was never lost sight -of; and no experiment was 

 recorded which suffered sufficient interruption to allow of the 

 above circumstance to transpire. In addition to this, the 

 samples of air, although they gave perfect satisfaction as to 

 the security of the vessels in which it was contained, were 

 operated on with little or no loss of time. The pressure and 

 temperature of the atmosphere were always reduced to one 

 common standard, viz. barometer 30 inches, and thermome- 

 ter 60°; and whenever the lower surface of the air in the jar 

 did not coincide with the exact level of the surface of the li- 

 quid in the trough, the density of the included gas was re- 

 duced to that of the external atmosphere. x 



The utmost care was had in the manufacture of the oxy- 

 gen, hydrogen, nitrous gas, &c. &c, that they might be of 

 the utmost purity. The oxygen was uniformly made from 

 the chlorate of potash in a green glass retort ; and although 

 the zinc of commerce was used for the manufacture of the 

 hydrogen, it was invariably purified by passing it immediately 

 before use through a solution of pure potash, for the purpose 

 of removing any carburetted hydrogen or other impurity, 

 and depriving it of any oxygen which it might contain, by 

 subjecting it to the influence of the spongy platina ball, heated 



