Black-Lead Pencils. The easiest way of producing, not only black-lead, but all sorts of pencils, is by the following process, which combines simplicity, cheapness, and quality. Take white or pipe-clay; put it into a tub of clean water, to soak for twelve hours, then agitate the whole, until it resembles milk ; let it rest two or three minutes, and pour off the supernatant milky liquor into a second vessel; allow it to settle, pour off the clear and dry the residue on a filter. Then add black-lead any quantity. Powder it and calcine it at a white heat in a loosely-covered crucible ; cool and Carefully repulvcrize, then add prepared clay, prepared plumbago, equal parts. Water to mix. Make them into a paste, and put it into oiled moulds of the size required; dry very gradually, and apply sufficient heat to give the required degree of hardness; lastly, the pieces should be taken carefully from the moulds and placed in the grooves of the cedar. The more clay and heat employed, the harder the crayon; less clay and heat of course produces a contrary effect. The shade of black may also be varied in the same way. Each mould must be made of four pieces of wood nicely fitted together.