HYDROGEN. 53 



portions, and mixing only one part of oxygen gas 

 with two of hydrogen. The report will then be 

 much louder than with common air. 



This experiment may be made conveniently by 

 means of an apparatus called the hiflammahle air pis- 

 tol. To charge it, nothing more is necessary than to 

 introduce its mouth inverted into a wide-mouthed 

 bottle, filled with a mixture of oxygen and hydro- 

 gen gas, leaving it in for a few seconds ; it is then 

 to be stopped with a cork, and may be fired by the 

 electrical spark taken from the prime conductor of 

 the machine, or by a charged Ley den phial. 



It has been, with great plausibility, conjectured, 

 that the noise of thunder is the effect of the rapid 

 combustion of hydrogen and oxygen gas, fired by 

 the electric spark ; and that the rain which falls so 

 copiously at the time of thunder-storms, is owing 

 to a sudden formation of water by this means. 



From its Hghtness, it has been employed for 

 making air-balloons, which have been already de- 

 scribed. 



Soap-bubbles, filled with hydrogen gas, ascend 

 in the air. To show this, fill a bladder with hydro- 

 gen gas, and fasten it to a tobacco-pipe ; dip the 

 bowl of the pipe into a lather of soap, squeeze the 

 bladder gently, in order to form a bubble, and de- 

 tach it in the usual manner. These bubbles will 

 rise rapidly into the air : if a lighted taper be pre- 

 sented to them, they catch fire and burn with a 

 slight explosion. 



If the bladder be filled with a mixture of hydro- 

 gen and common air, the soap-bubbles will ascend, 

 and when the taper is presented to them they will 

 explode with a loud report. This experiment is 

 more striking if oxygen gas be mixed with 

 hydrogen. If the bladder be squeezed so as to 



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