The different sorts of gunpowder are usually distinguished by marks on the heads of the barrels. Gunpowder marks are various. All gunpowder for service is mixed in proportions according to its strength, so as to bring it as much as possible to a mean and uniform force. This sort of powder, says Adye, (_Bombardier and Pocket Gunner_,) is marked with a blue L. G. and the figure 1/2; or with F. 1/2 G. and the figure 3, whose mean force is from 150 to 160 of the eprouvette. This is the powder used for practice, for experiments, and for service. The white L. G. or F. G. is a second sort of powder of this quality. It is sometimes stronger but not so uniform as the L. G. It is, therefore, generally used in filling shells, or such other things as do not require accuracy. The red L. G. F. G. denotes powder in the British service, made at the King's mills, with the coal made in cylinders, and is used at present only in particular cases, and in comparisons, and to mix with other sorts to bring them to a mean force. The figures 1, 2 or 3 denote that the powder is made from saltpetre, obtained from the rough. Other marks are also in use to designate the rifle, musket, cannon powder, and the like. Powder merchants recover damaged gunpowder, by putting a part of the powder on a sail cloth, and adding an equal quantity of good powder, which is well mixed with it, and the mixture is then dried. _Sec. VIII. Of Lampblack._ Lampblack, which is nothing more than a finer kind of coal, is so named from its being produced and originally made by the combustion of oil in lamps. It is hardly necessary to say, that it is formed in the combustion of turpentine, various species of the _pinus_, tar, pitch, rosin, &c. as all these substances yield it more or less, and of different qualities. It is the result of imperfect combustion; for, if the combustion were rapid, and the smoke itself consumed, we would then have only carbonic acid. This fact is exemplified in the argand lamp, which, on account of the glass cylinder, consumes its own smoke. The process of forming lampblack is conducted in _lampblack houses_. After the combustion has ceased, the soot or lampblack is swept down, as it collects above and on the sides of the room. When it is obtained by burning the dregs and coarser parts of tar, furnaces of a particular construction are used. The smoke is conveyed through tubes into boxes, each covered with linen, in the form of a cone. Upon this linen the soot is deposited, from which it is, from time to time, beaten off into boxes, and afterwards packed in barrels for sale. There is also a very fine black, superior in many respects to lampblack, especially in making the ink for copperplate printers, prepared by carbonizing grape stalks, &c. in close iron vessels.