Day after day, destruction by a "close smothering heat" went on. Slowly the pile sank until suddenly the top fell in, and a white fla roared upwards as if it were a spirit which had been trying so long to escape; and in its unexpected freedom it endeavoured to leap over the surrounding trees. And then tar began to flow, passing through the hole in the platform into & barrel placed beneath. Naturally, how long tar would flow depended on the size of the wood pile; the process of distillation might go on for several weeks.
But such a crude and wasteful method of producing the viscid substance was sure to be improved upon as time went on; and, in Russia, I think it was, closed stills or retorts were used. It proved to be far more economical, 20 per cent. of far being produced as against 17 per cent. by the old method. Further, many of the by-products were saved, and gas given off was collected and used in heating the retorts.
By wading through a little chemistry I began to understand why tar and the fumes from a bottle of old and mild settled down together so well I had always looked upon tar as being an honest-to-goodness stuff, until one day I discovered it was teeming with all manner of complexities. It contained so many things with most frightening names. Pyroligneous acid is one example, although this has a more homely name—acetic acid. Yet, what can one expect from a "semi-fluid substance of a dark brown colour... possessing a sharp taste" when told that it is a mixture of homologous hydrocarbons? Not even ordinary hydro-carbons!
Now, to you among yachtsmen who walk by sri honest longshoreman busy with a brush and a pot of "gas-house paint" and feel superior because of the tin of best anti-fouling you carry—don't wrinkle your nose in distaste, but remember that no less a person than an eari—the Earl of Dundonald—spent much time and thought endeavouring to distin tar from coal. He succeeded; and then he patented the process in the year 1787. Some persons maintain that it was in the year 1781 that the chemist, Becher, produced tar from coal, using the Earl of Dun-donald's patent.
Since then, with the general use of coal gas. tar became rather an unwanted product until the invention of "tar-colours" when a man might preserve the fence round his garden without it becoming horribly black and messy.
Text read from the printed page and cleaned; old type leaves the occasional error.