GAS COMPRESSED. 307 



the square inch. This amount of pressure on every square 

 inch of a vessel of the size of a barrel, for example, would 

 constitute an enormous bursting force a f force of forty or 

 fifty thousand pounds ! 



It is on this principle, however, that the copper cylinders 

 in the gas wagon shown in the engraving were filled, and 

 yet so prodigiously heavy and strong were they made, that 

 sometimes, as has already been said, ten or twelve volumes 

 of gas were forced into them. If the number is taken as 

 eleven, then, allowing one to balance the ordinary atmos- 

 pheric pressure on the outside, we should have an expan- 

 sive force of a hundred and fifty pounds to the square inch 

 acting all the time upon the interior surfaces of all the cyl- 

 inders. 



The gas, in this compact form, was conveyed about the 

 city and delivered to the consumers. Those who chose to 

 take their gas of this company, of course, were obliged to 

 provide the means of receiving it in the form of a gasome- 

 ter, or of some very strong and well-secured receptacle, for 

 the cylinders in the wagon were altogether too massive, 

 solid, and heavy to be removed. When the wagon arrived 

 at the door of one of the customers, a pipe from one of the 

 cylinders in the wagon was connected with one communi- 

 cating with the reservoir within, and then, when the stop- 

 cock was open, the gas from the cylinder would rush in by 

 its own expansive force until the quantity in the two re- 

 ceptacles was equal that is, in case the receptacles them- 

 selves were equal and the pressure would be that of five 

 atmospheres in each. 



Then, of course, no more would flow from that cylinder, 

 but an additional quantity could be thrown in from a fresh 

 cylinder where the pressure of the whole ten atmospheres 

 was still entire. The first cylinder, moreover, which had 

 delivered half its gas, could be made to deliver more at 





