354

DESCRIPTION OP THE PLATES.

the tube in the centre of the vessel. The glass vessel, b. is thendepressed till the coincidence of the Zero point of the graduatedrod, d, with the aperture, x. indicates its total emersion. Thisbeing done, a communication is then made between the tube,c c. and the apparatus from which the gas proceeds, by openingeither of the cocks, and letting the other be shut. The gas, thusintroduced, will of course proceed by the tube, c c. and enter thevessel, b. which, as it becomes filled, will emerge by the pres-sure of the gas. For breathing or transferring gases from thisapparatus, a flexible tube, e. may be joined to either of the stop-cocks, and the quantity of gas expended will be measured by thegraduated tube, d.

PLATE. II. *

Fig. 1...A table furnace, formed of two large black-lead cru-cibles, a. b. The lower one, out of which the bottom is cut,and which is furnished with a grate, is fixed into a circular sup-port of strong sheet iron, c. furnished with two handles for theconvenience of removing it. This part of the furnace forms theash-pit, and is furnished with a door. The upper crucible has ahole cut in its bottom, into which is inserted an iron tube, d. (ofwhich part is shown in the drawing) forming the chimney of thefurnace, which may be elongated occasionally by an additionalpiece, so as to increase the draft at pleasure. In order to renderthis furnace less liable to accidents, a strong iron hoop, e e. isfastened round each of the crucibles, the lower of which serves tosecure the junction of the two crucibles. In the upper and lowerpart of the furnace is cut a semi-circular opening for the intro-duction of charcoal or coke, according to the different processescarried on in the furnace; and the pieces of the crucible, thusremoved, may serve as doors to the opening. If an iron sand-bath, with a rim, (which is furnished with the furnace) be

* Facing the title page of vo). ii.