comprehending practical illustrations of the machinery and processes employed in every description of manufacture of the British Empire.
With nearly Two Thousand Engravings.
By Luke Hebert, civil engineer, edifor of the History and Progress of the Steam Engines, Register of Arts and Journal of Patent Inventions, etc.
In two volumes.
VOL. II.
London: Thomas Kelly, 17, Paternoster Row.
MDCCCXXXVI (1836).An instrument used by painters for laying on their colours; they are of various kinds. The larger sorts are made of boars' bristles, the thick ends of which are bound to a stick, large or small, according to the uses they are designed for; these, when large, are termed brushes. The finer sorts of pencils are made of camels' hair, also badgers' and squirrels' hair, and of the down of swans; these are tied at the ends by a piece of thread to keep the hair from spreading, and the other ends are enclosed in the barrels of quills of various sizes, suited to the pencil, some of which are of small birds, as those used for drawing lines, and in miniature painting. The usual test of a good pencil is to draw it between the lips, when it should come out with a sharp, conical, and, as it were, solid point.
Pencil is also an instrument used for drawing and writing, made of long slips of black-lead, chalk, or crayon, placed in a groove made in the centre of a stick of wood, usually cedar, on account of the facility of cutting it. The very common black-lead pencils that are hawked about are a composition of powdered black-lead and melted sulphur. Their melting, or softening, or yielding a bluish flame, on application to the Same of a candle, betrays their composition. The genuine black-lead pencils are made of the fine Cumberland plumbago, sawed into slips, fitted into the grooves, and having another piece glued over them. The pure plumbago is, it is said, too soft to enable an artist to make a fine line; to produce this effect, a hard resinous matter is intimately combined with the lead in the following way, which is said to be the invention of Mr. Cornelius Valley. Fine Cumberland lead, in powder, and shell-lac are first melted together by a gentle heat. This compound is then reduced to powder .again and re-melted; then powdered again and re-melted, until both substances are perfectly incorporated, and it has acquired a perfectly uniform consistence. The mass is then sawed into slips, and glued into the cedar mountings in the usual manner of making other black-lead pencils. To render them of various degrees of hardness, the materials are differently proportioned; the hardest having the most shell-lac, the softer but very little, and the softest none; and their blackness is increased in proportion to their softness.
Mordan's "ever-pointed pencils" were the subject of a patent granted to Hawkins & Mordan, in 1823. The pencil-case has a slider, actuated by a screw for the purpose of projecting forward a little cylinder of black-lead, as it wears away, which is done by holding the nozzle in one hand, and turning round the pencil-case with the other, the thickness of the lead being so small as not to need cutting for the ordinary purposes of a pocket-pencil. Fig 1 in a section of the pencil-case; A the black-lead or crayon, encompassed by the nozzle, which, with the whole of the case, is made of metal, usually silver. B is the driver, being a hollow cylinder with a screw-thread round a part of it; at the end of this screw the black-lead is inserted and held fast; C is the elon gated part of the driver, which passes through the guide D; at E, within the outer case, is another cylindrical piece, connected to the nozzie at one end, and having at the other a hollow screw that works round on the thread of the driver B, and, as it turns, causes the projector to advance or recede, as may be required. These pencil-cases have had an immense sale, and have been improved upon in a variety of ways during the last ten years.
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