FIRE-CLAY AKD ANTHRACITE. 41 



there ; and one of the advantages justly claimed by Mr. Fletcher 

 is, that with his solid fire-clay bottom there will be nounburned 

 cinders nothing left but the incombustible mineral ash of the 

 coal. Economy and abatement of smoke are the necessary 

 concomitants of such complete combustion. 



A valuable " wrinkle" was communicated by Mr. Fletcher. 

 The powdered fire-clay that is ordinarily sold is not easily 

 applied on account of its tendency to crumble and peel off the 

 back and sides of the stove after the first heating. In order 

 to overcome this, and obtain a fine compact lining, Mr. 

 Fletcher recommends the mixing of the fire-clay powder with 

 a solution of water-glass (silicate of soda) instead of simple 

 water. It acts by forming a small quantity of glassy silicate of 

 alumina, which binds the whole of the clay together by its fu- 

 sion when heated. 



Londoners, and, in fact, Englishmen generally, have hitherto 

 regarded anthracite as a museum mineral and a curiosity, rather 

 than an every-day coal-scuttle commodity. If it is to be the 

 fuel of the future, it is very desirable that we should all know 

 something about its merit and demerits, as well as the possi- 

 bilities of supply. 



Anthracite is a natural coke. From its position in the earth, 

 and its relations to bituminous coal, as well as from its com- 

 position, we are justified in regarding it as a, coal that was 

 originally bituminous, but which has been altered by heat, 

 acting under great pressure. In the great coal-field of South 

 Wales, to which we must look for our main supply of anthra- 

 cite, we are able to trace the action of heat in producing a 

 whole series of different classes of coal in a single seam, which 

 at one part is highly bituminous soft, flaming coal, like the 

 Wallsend, then it becomes harder and less bituminous, then 

 semi-bituminous " steam coal," then less and less flaming 

 until at last we have the hard shiny form of purely carbona- 

 ceous coal, that may be handled without soiling the fingers, 

 and which burns without flame, like coke or charcoal. This 

 change proceeds as the seam extends from the east toward the 

 west. In some places the coal at the base of a hill may be 

 anthracite, while that on the outcrop above it may be bitu- 

 minous. 



An artificial anthracite may be made by heating coal in a 

 closed vessel of sufficient strength to resist the expansion of the 

 gases that are formed. It differs from coke in being com- 



