1800.] On the Coal Trade. 325

Durham, by the Hon. and Rev. James Cochrane, as follows. [ am your humble ſervant, Ae e

T is generally known that wood firſt decays juſt above and

below the ſurface of the gróund. Neither ſurface-painting, burning, or pitch, will preſerve it ſo well as the following me- thod, of indenting or pundQuring it with an inſtrument ſhaped like a caulking-iron with one, two, or three rows of teeth.

In the preſent method of uſing paint, tar, or pitch, as 2 pre- ſervative of wood, they have only ſurface- hold of it, whereas in that here propoſed, ſuch paint, tar, or pitch may be let into the grain of the wood to any depth, by indenting it at right angles to its plane. The ſtrength of timber, by this operation is by no means diminiſhed, but completely fortified againſt in- jury from alternate wet or dry. The punéturing irons here mentioned are manufa@ured and ſold’ by Mr. Gill, gunſmith at Richmond in Yorkſhire. They may be uſed to great advan- tage in ſhip building, with coal-tar or-pitch, and are well calcu- lated to preſerve the flood-gates of canals, lining of docks, water wheels, and poſts upon highways. When theſe inſtruments are uled, the wood ought to be well ſeaſoned. It muſt be firſt punétured, then warmed, and laftly done over with coal pitch or paint, ſo as to fill up the punQures.

Was the wood to be pitched cold, the air in the pundure, will prevent the admiſſion of the pitch or paint. In all new in- cloſures where ſtake fences are uſed, the plan here propoſed, will make them laſt until the quick-ſet hedge has grown up ſuífciently.

Mansfield, Fan. 19th, 1795. FC

ON THE COAL TRADE.

For the Commercial and Agricultural Magazine. MR. EDITOR.

OUBTLESS your obſervation"of. the frequency of vulgar

errors, muſt have informed you, how great a benefit is conferred on the public, by thoſe who try to sradicate ſuch as are too frequently injurious to the intereſts of the community. Even national reputation is augmented with national information; and in no fubjeds are general errors ſo frequent, as in‘thoſe of fre- quent uſe, and thercfoie moſt frequently diſcuſſed by ignorant pretenders, or taken for granted, without any diſcuſſion.

A general error in the eſtimation of the fuel of Lo:'on, of Newcaftle coal,‘is what local information enables me to develope without hefitation or difidence. In the London market, coal is Known to be divided into deft, ſecond and inferior coal. etwixt the prices of theſe different deſcriptions, therè is uſually five or fix ſhillings difference in price, Paradoxical as it May appear,