Some Physical Properties of Coal

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The behaviour of coal in the different circumstances under which it is used is so varied and complex, and yet of so much importance to our well-being, that I offer no apology for recording observations made with regard to its physical properties and behaviour. If we first examine the different conditions under which coals are used, and then examine the properties of the coals which have been found best suited to these conditions, we shall learn at least something of the general principles which should guide us in the selection of coals for our different requirements; and, on the other hand, we may, from the behaviour of the coal whilst in use, gather some information as to its origin and the alterations to which it has been subjected since it was deposited. In this country some coals are used in open fire grates for domestic purposes which burn at a comparatively low temperature, some in boiler furnaces at a higher temperature for the making of steam, and others in reverbatory furnaces at a very high temperature for the heating or smelting of glass, iron, steel, &c. These are all used with a free admission of air. Again, other coals are used for gasmaking, which I may remind you is performed by the introduction of coals into an air-tight vessel, this, being heated, distils its contents, giving off gas and other substances and leaving a residue of somewhat spongy coke. Other coals are used for nothing but making coke. In this ...