142 FARADAY 



use too small a charge the first portion of the gas will be 

 mixed with the air already in the retort, and I should be 

 obliged to sacrifice the first portion of the gas because it 

 would be so much diluted with air; the first portion must 

 therefore be thrown away. You will find in this case that 

 a common spirit-lamp is quite sufficient for me to get the 

 oxygen, and so we shall have two processes going on for 

 its preparation. See how freely the gas is coming over 

 from that small portion of the mixture. We will examine 

 it and see what are its properties. Now in this way we are 

 Q producing, as you will observe, a gas just like the one 

 we had in the experiment with the battery, transparent, 

 undissolved by water, and presenting the ordinary vis- 

 ible properties of the atmosphere. (As this first jar 

 contains the air, together with the first portions of the 

 oxygen set free during the preparation, we will carry it 

 out of the way, and be prepared to make our experi- 

 ments in a regular, dignified manner.) And inasmuch 

 as that power of making wood, wax, or other things 

 burn, was so marked in the oxygen we obtained by 

 means of the voltaic battery from water, we may expect 

 to find the same property here. We will try it. You 

 76' see there is the combustion of a lighted taper in air, and 

 here is its combustion in this gas [lowering the taper into 

 the jar.] See how brightly and how beautifully it burns! 

 You can also see more than this: you will perceive it is 

 a heavy gas, while the hydrogen would go up like a balloon, 

 or even faster than a balloon, when not encumbered with 

 the weight of the envelope. You may easily see that although 

 we obtained from water twice as much in volume of the 

 hydrogen as of oxygen, it does not follow that we have twice 

 as much in weight, because one is heavy and the other a 

 very light gas. We have means of weighing gases or air; 

 but, without stopping to explain that, let me just tell you 

 what their respective weights are. The weight of a pint of 

 hydrogen is three quarters of a grain; the weight of the 

 same quantity of oxygen is nearly twelve grains. This is a 

 very great difference. The weight of a cubic foot of hydro- 

 gen is one twelfth of an ounce; and the weight of a cubic 

 foot of oxygen is one ounce and a third. And so on we 



