78 



that's it : 



brace 5 retort houses, containing 1 ,900 retorts 

 and 14 telescopic gas-holders, of the aggre- 

 gate capacity of 4,039,000, cubic feet. The 

 quality of the gas is determined by daily pho- 

 tometric observations at the corner of Irving 

 Place and 15th street. The annual consump- 

 tion of gas coal is 76,000 tons, and 200,000 

 bushels of hydrate of lime are used for puri- 

 fying the gas. 



The use of gas has continued to spread 

 among the chief cities and towns of the Uni- 

 ted States with great rapidity, especially in 

 the last few years, till the gas interest, it is 

 estimated, now represents a capital of $34,- 

 920,000 in the United States, divided among 

 237 companies ; and in Canada, $1,040,000 

 among 6 companies. 



The lowest price an v where paid for gas is 

 at Pittsburgh, Pa., $1 50 per 1,000 cublic feet. 

 The highest price, $7 00, is paid at Auburn 

 and Watertown, N. Y., Belfast, Me., Char- 

 lotte, N. C, and some other places. 



construction of gas- 

 hurners of the best 

 . - , description, the prin- 

 V / ciple of the Argand 



lamp, 315, is still pre- 

 served. In some of 

 them a button, 20, 

 has been inserted, to 

 throw open the circle 

 of flame. When the 

 circular, or Argand 

 flame, is not adopted, 

 an endeavour is made 

 to spread the flame, 

 by other means, so as to increase 

 the light. This is effected by 



330. 



cock-spur, 2, in which there are 

 three jets of gas issuing from 

 separate holes ; the bafs-wing, 3, 

 from which the gas escapes through 

 a slit ; and the union, 4, in which 

 there are are a number of holes in- 

 stead of a slit. The object of 

 each contrivance is to present as 

 large a surface of flame as pos- 

 sible to the surrounding air, so 

 that the oxygen of the air may 

 combine with the elements of the 

 flame, and by heating the small 

 particles of carbon to incandes- 

 cence* increase the brilliancy of 

 the light. 



Gas may be made of other 

 substances besides coal and oil: 

 wood, resin, peat, wine-lees and 

 grape-skins, tar, and even water, 

 may be converted into gas, and 

 applied variously to purposes of 

 lighting and heating. Naphtha 

 forms a sort of port- i 

 able gas, 1, frequently 

 burnt by stall-keep- 

 ers. The naphtha is ^ 

 placed in the reser- 

 voir, 2, from which it 

 runs through the tube, 

 3 ; a small tap, 4, is 

 used to regulate or 

 stop the supply. A 

 light being applied, 

 the pipe soon becomes hot ; and 

 as the naphtha reaches the heated 

 burner, 5, it becomes volatilized,^ 

 and forms jets of gas. But, of 

 various substances, coal is the 

 most economical, and can be ob- 

 tained in the greatest abundance. 



Let us now consider — What is 

 coal? It consists of the mine- 

 ralized substance of vast forests, 



331. 



various kinds of burners, 1 ; the 



* A state of glowing white heat 

 t Exhaled in a state of vapour. 



