Fig. 4.
The tube v, [Fig. 1], is for carrying away vapour, if necessary. This tube may be opened or closed by means of a damper moved by the little handle shown on the right. The heat of the roaster is regulated by means of the register c, [Fig. 4], in the ash-pit door of the fire-place, its dryness by the above-named damper of the steam tube v, and also by the blowpipes, b p.
These are iron tubes, about 2½ in. in diameter, placed underneath, so as to be in the midst of the flame as it ascends from the fire into the enveloping flue, shown by the dotted lines, [Fig. 4], where their external openings are shown at b p, b p, and the plugs by which they may be opened or closed in [Fig. 1]. It is evident that by removing these plugs, and opening the damper of the steam pipe, a blast of hot dry air will be delivered into the roaster at its back part, and it must pass forward to escape by the steam pipe. As these blowpipes are raised to a red heat when the fire is burning briskly, the temperature of this blast of air may be very high; with even a very moderate fire, sufficiently high to desiccate and spoil the meat if they were kept open during all the time of cooking. They are accordingly to be kept closed until the last stage of the roasting is reached; then the fire is urged by opening the ash-pit register, and when the blowpipes are about red-hot, their plugs are removed, and the steam-pipe damper is opened for a few minutes to brown the meat by means of the hot wind thus generated.
It will be observed that a special fire directly under the roaster is here designed, and that this fire is enclosed in brickwork. This is a general feature of Rumford’s arrangements. The economy of the whole device will be understood by the fact that in a test experiment at the Foundling Institution of London, he roasted 112 lbs. of beef with a consumption of only 22 lbs. of coal (three pennyworth, at 25s. per ton).
Rumford tells us that ‘when these roasters were first proposed, and before their merit was established, many doubts were entertained respecting the taste of the food prepared in them,’ but that, after many practical trials, it was proved that ‘meat of every kind, without any exception, roasted in a roaster, is better tasted, higher flavoured, and much more juicy and delicate than when roasted on a spit before an open fire.’ These italics are in the original, and the testimony of competent judges is quoted.
I must describe one experiment in detail. Two legs of mutton from the same carcass made equal in weight before cooking were roasted, one before the fire and the other in a roaster. When cooked, both were weighed, and the joint roasted in the roaster proved to be heavier than the other by 6 per cent. They were brought upon table at the same time, ‘and a large and perfectly unprejudiced company was assembled to eat them.’ Both were found good, but a decided preference given to that cooked in the roaster; ‘it was much more juicy, and was thought better tasted.’ Both were fairly eaten up, nothing remaining of either that was eatable, and the fragments collected. ‘Of the leg of mutton which had been roasted in the roaster, hardly anything visible remained, excepting the bare bone, while a considerable heap was formed of scraps not eatable which remained of that roasted on a spit.’
This was an eloquent experiment; the gain of 6 per cent. tells of juices retained with consequent gain of flavour, tenderness, and digestibility, and the subsequent testimony of the scraps describes the difference in the condition of the tendonous, integumentary portions of the joints, which are just those that present the toughest practical problems to the cook, especially in roasting.