136 Traxsactions of the American Institute. 



same time cools the gas. To insure success a second arrangement of 

 this kind is adjusted, and the rain descends and the impurities flow 

 into the reservoir below. Then we have instruments which relie^'e the 

 retorts from pressure, and there is a beaiitiful mechanism hy which the 

 gas is passed under water, and valves are so arranged that the 

 water may be changed but the gas will not escape. Here we 

 have the method of puritying it, with a series plates of lime. 

 The gas is then received into the large meter, where the 

 amount is determined, and then into the grand reservoir. AYlien 

 I tell you that a single company in the city of Kew York 

 makes 4,000,000 cubic feet of gas every twenty-four hours, you 

 "will have some conception of the magnitude of the scale on which 

 this operation is conducted. From this it passes through a regulator 

 or governo]", and is distributed through the city. I have not time to 

 enter into all the details ; but this is the beautiful mechanism by 

 which is generated the gas which we constantly employ. Lest I 

 should be inaccurate, I called, the other day, upon the Manhattan 

 Gas Company, and they stated that they made, last year, 1,250,000,000 

 cubic feet of gas. The other companies — the jS'ew 1l ork, the Metro- 

 politan, and the Harlem Company, associated with it — produced 

 about 2,700,000,000 cubic feet of gas the last year. If we estimate 

 this at the price of the gas of the Manhattan Company, which is three 

 dollars per 1,000 feet, this amounts to nearly $8,250,000. If we con- 

 sider that about 20 per cent is lost by leakage and in other ways, we 

 have at least $6,500,000 expended in the production of gas- for illu- 

 minating purposes ; and this in one city! AVe can hardly fail to be 

 reminded of that astounding proposition of our great philosopher, 

 Franklin, who proposed to save England millions of dollars annually, 

 in this way : " Let people go to bed half an hour after sunset, and 

 rise half an hour before sunrise." Let us not forget that in the great 

 coal strata we have stored up the forces of the light which originally 

 shone upon the earth. It may have been light which surrounded or 

 invested our globe, or that received from afar. 



We can produce light by chemical means, far surpassing anything 

 which I have yet shown to you. It is simply by the galvanic battery. 

 You are all familiar with the fact that by putting acids and metals 

 together, or any substances that have a chemical affinity, we have 

 certain powers .revealed. Here is a cell of the form which we shall 

 use this evening; a glass jar containing about 1^ gallons of water, 

 with a zinc cylinder, and a porous cup, and slab of carbon. Within 



