ATTEWDIN© THE FOBMATION OT OOAL, fcc, 277 



red-hot material through which they are obliged to pass, 

 and by which they deposit their carbon, and are eliminated 

 as pure hydrogen, a gas which forms from 30 to 40 per cent, 

 of coal gas, and is utterly useless in the illumination. 



The production of hydrogen and tar are manifest evi- 

 dence that the heat employed is too great at the surface of 

 the coal, and too low in the centre of the mass. 



When gas is made from resin, or from oil, the melted 

 resin or the oil is allowed to fall in thin steamlets on a red- 

 hot plate, or to trickle over a .more extensively heated sur- 

 face. The facility with which resin or oil is converted into 

 volatile liquids, renders necessary a somewhat ample sur- 

 face, in order that these liquids may be decomposed into gas. 



There are some furnaces to steam-boilers in which the fuel 

 is burnt with limited access of air, and is supplied to the 

 furnaces by means of hoppers, the coal, in a somewhat finely 

 divided state, falling on a revolving horizontal plate, and 

 being by this scattered in a thin layer on the incandescent 

 matter within. 



This method of supplying the furnaces is not found to be 

 profitable, and for a very sufficient reason: the coal, in the 

 first instance, is simply distilled, and the gases eliminated 

 meeting with little or no oxygen within the furnace, pass 

 off undecomposed, and the heat that would arise from their 

 combustion is not only lost, but the gases impinging on the 

 bottom of the boiler reduce its temperature, and lower the 

 tension of the steam. If no air whatever were admitted to 

 the furnace, the coal would then be placed in exactly the 

 same condition as the resin and oil which have been used 

 for gas-making. 



The course of the research indicated by the analysis of 

 the subject of gas-making so far completed is obvious. These 

 are the determination of the constituents of the coals and 

 cannels to be employed as materials ; a rigid examination 

 of the products, gaseous, liquid, and solid, resulting firom 



