238 Mr GRAHAM on the Law of 



the receiver, and stopping exactly when it attained a tension of 

 three inches. 



Air entered, according to eight or ten experiments made on 

 different days, in within ten seconds, more or less, of ten minutes, 

 and so whether the air was saturated with aqueous vapour or 

 dry. 



The same volume of different gases entered in the times ex- 

 pressed in the following table, under the same pressure, or be- 

 ginning at a pressure of 29 inches mercury, and terminating 

 with a pressure of 27 inches : 



.* 



Minutes. Seconds. 



Air, dry, - - 10 ... 



Air, saturated with moisture at 60, - 10 ... 



Carbonic acid, - - - 10 ... 



Nitrogen, - - - 10 ... 



Oxygen, - - - 10 ... 



Carbonic oxide, - - - 9 ... SO 



Olefiant gas, - - - - 7 ... SO 



Coal gas, - - - 7 ... 



Hydrogen, - - - 4 ... 



In repetitions of the experiments, the numbers oscillated 10, 

 or 12, sometimes 20 seconds, on either side of the numbers given 

 in the table, from circumstances which could not easily be appre- 

 ciated. As the mercury in the gauge fell not continuously, but 

 by leaps, from adhesion to the glass, the experiments are not 

 susceptible of the greatest accuracy. 



The greater the pressure the more rapidly are gases forced 

 through the pores of the plug ; but the quantity of gas which 

 penetrates in any given time is not exactly proportional to the 

 pressure, at least in the case of air and hydrogen. By doubling 

 the pressure, we do not quite so much as double the quantity of 

 gas forced through ; or a fixed quantity of gas does not enter in 



