An especially fine quality of lamp-black is obtained from bone-oil, deprived of the ammonia with which it is always contaminated. It is manufactured on a commercial scale by means of the apparatus shown in Figs. 3 and 4. The oil is contained in the lamp A and kept at a constant level by means of the globular vessel B, which is also filled with oil and inverted over A. The oil flows from the lamp into the tube C, which is bent upwards at the farther extremity on a level with the oil in the lamp. A cotton wick is supplied to the bent end of the tube, as well as a little spout D, for conducting away any oil that may overflow into the receptacle E placed beneath. A conical hood _a_ surrounds the flame of the lamp and terminates in a tube _b_, through which are conveyed the sooty products of the combustion of the oil into the wide lateral tube _c_, arranged to accommodate the smoke from about a dozen such lamps placed at intervals of about 6 feet, as indicated in the figures. The effect of this wide tube _c_ is not only to cool the smoke, but also to collect the water and other liquids condensed. The smoke and vapours pass hence into _d_, the first of a series of sacks made of closely woven linen, about 10 or 12 feet long and 3 feet in diameter, closed at the bottom with a trap or slide _e_, and formed at the upper and lower ends of sheet-copper tubing made funnel-shaped. The upper one of these is prolonged into an additional pipe _f_, by means of which the smoke arrives at the second sack _g_ in the series, thence finding its way to the third, and so on till the last sack of the row is reached. In connection with the last sack of each row is placed a horizontal flue F, in which are arranged frames covered with wire gauze and mounted on hinges. Their purpose is to retain the small remaining portions of lamp-black passing out with the smoke from the sacks. The meshes of the gauze are constantly getting filled up with soot, which necessitates a periodical checking of the draught for its removal. This is done by means of the rod G, which, when raised and allowed to fall suddenly, jerks the accumulated mass off the gauze. The current of air passing through the entire apparatus can be regulated by a damper placed at the entrance to the chimney in which the flue F embouches. At regular intervals, the mouthpieces in the lower ends of the sacks are removed, and their contents are shaken out separately and collected according to their various qualities. That gathered from the first sack in each row should always be kept apart from the remainder, as it is much contaminated by the presence of resinous and tarry matters. [Illustration: Fig. 5.--APPARATUS FOR MAKING LAMP-BLACK.]