Part II. of Count Rumford’s ‘Tenth Essay’ is devoted to his roaster

and roasting generally, and occupies ninety-four pages, including the special preface. This preface is curious now, as it contains the following apology for delay of publication: ‘During several months, almost the whole of my time was taken up with the business of the Royal Institution; and those who are acquainted with the objects of that noble establishment will, no doubt, think that I judged wisely in preferring its interest to every other concern.’

To those who attend the fashionable gatherings held on Friday evenings in ‘that noble establishment’ during the London season, it is almost comical to read what its founder says concerning the object for which it was instituted—viz. the noble purpose of DIFFUSING THE KNOWLEDGE AND FACILITATING THE GENERAL INTRODUCTION OF NEW AND USEFUL INVENTIONS AND IMPROVEMENTS.’ The capitals are Rumford’s, and he illustrates their meaning by reference to ‘the repository of this new establishment,’ where specimens of pots and kettles, ovens, roasters, fireplaces, gridirons, tea-kettles, kitchen-boilers, &c., might be inspected.

Some years ago, when I was sufficiently imprudent to accept an invitation to describe Rumford’s scientific researches in _one_ Friday evening lecture, rigidly limited to fifty-seven minutes (and consequently muddled my subject in the vain struggle to condense it), I tried to find the original roaster, but failed; all that remained of the original ‘repository’ being a few models put out of the way as though they were empty wine-bottles. I am not finding fault, as the noble work that has been done there by Davy, Faraday, and Tyndall must have profoundly gladdened the supervising soul of Rumford (supposing that it does such spiritual supervision), in spite of his neglected roaster, which I must now describe without further digression.

It is shown open and out of its setting in Fig. 1, and there seen as a hollow cylinder of sheet-iron, which, for ordinary use, may be about 18 inches in diameter and 24 inches long, closed permanently at one end, and by a hinged double door of sheet-iron (_dd_) at the other. The doubling of the door is for the purpose of retaining the heat by means of an intervening lining of ill-conducting material. Or a single door of sheet-iron, with a panel of wood outside, may be used. The whole to be set horizontally in brickwork, as shown in Fig. 4, the door-front being flush with the front of the brickwork. The flame of the small fire below plays freely all round it by filling the enveloping flue-space indicated by the dotted lines on Fig. 4. Inside the cylinder is a shelf to support the dripping-pan (_d_) Fig. 1, which is separately shown in Figs. 2 and 3.

This dripping-pan is an important element of the apparatus. Fig. 3 shows it in cross section, made up of two tin-plate dishes, one above the other, arranged to leave a space (_w_) between. This space contains water, half to three-quarters of an inch in depth. Above is a gridiron, shown in plan, Fig. 2, on which the meat rests; the bars of this are shown in section in Fig. 3. The object of this arrangement is to prevent the fat which drips from the meat from being overheated and filling the roaster with the fumes of burnt—_i.e._ partially decomposed, fat and gravy, to the tainting influence of which Rumford attributed the English prejudice against baked meat. So long as any water remains the dripping cannot be raised more than two or three degrees above 212°.

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 25_s._ 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.

But why are these roasters not in general use? Why did they die with their inventor, notwithstanding the fact, mentioned in his essay, that Mr. Hopkins, of Greek Street, Soho, had sold above 200, and others were making them?

Those of my readers who have had practical experience in using hot air or in superheating steam, will doubtless have already detected a weak point in the ‘blowpipes.’ When iron pipes are heated to redness, or thereabouts, and a blast of air or steam passes through them, they work admirably for a while, but presently the pipe gives way, for iron is a combustible substance, and burns slowly when heated and supplied with abundant oxygen, either by means of air or water; the latter being decomposed, its hydrogen set free, while its oxygen combines with the iron, and reduces it to friable oxide. Rumford does not appear to have understood this, or he would have made his blowpipes of fire-clay or other refractory non-oxidisable material.

The records of the Great Seal Office contain specifications of hundreds of ingenious inventions that have failed most vexatiously from this defect; and I could tell of joint-stock companies that have been ‘floated’ to carry out inventions involving the use of heated air or super-heated steam that have worked beautifully and with apparent economy while the shares were in the market, and then collapsed just when the calls were paid up, the cost of renewal of superheaters and hot-air chambers having worse than annulled the economy of working fuel described in the prospectus. Thus a vessel driven by heated air, as a substitute for steam, was fitted up with its caloric engine, and crossed the Atlantic with passengers on board. The voyage practically demonstrated a great saving of coal; the patent rights were purchased accordingly for a very large amount, and shares went up buoyantly until the oxidation of the great air chamber proved that the engine burned iron as well as coal at a ruinous cost.

Although no mention is made by Rumford of such destruction of the blowpipes, he was evidently conscious of the costliness of his original roaster, as he describes another which may be economically substituted for it. This has an air chamber formed by bringing down the body of the oven so as to enclose the space occupied by the blowpipes shown in Fig. 1, and placing the dripping-pan on a false bottom joined to the front face of the roaster just below the door, but not extending quite to the back. An adjustable register door opens at the front into this air chamber, and when this is opened the air passes along from front to back under the false bottom, and rises behind to an outlet pipe like that shown at _v_, Fig. 1. In thus passing along the hot bottom of the oven the air is heated, but not so greatly as by the blowpipes, which being surrounded by the flame on all sides, are heated above as well as below, and the air in passing through them is much more exposed to heat than in passing through the air-chamber.

To increase the heat transmitted in the latter, Rumford proposes that ‘a certain quantity of iron wire, in loose coils, or of iron turnings, be put into the air chamber.’

This modification he called a ‘roasting-oven,’ to distinguish it from the first described, the ‘roaster.’ He states that the roasting-oven is not quite so effective as the roaster, but from its greater cheapness may be largely used. This anticipation has been realised. The modern ‘kitchener,’ which in so many forms is gradually and steadily supplanting the ancient open range, is an apparatus in which roasting in the open air before a fire is superseded by roasting in a closed chamber or roasting-oven. Having made three removals within the last twelve years, each preceded by a tedious amount of house-hunting, I have seen a great many kitchens of newly-built houses, and find that about 90 per cent. of these have closed kitcheners, and only about 10 per cent. are fitted with open ranges of the old pattern. Bottle-jacks, like smoke-jacks and spits, are gradually falling into disuse.

When these kitcheners were first introduced, a great point was made by the manufacturer of the distinction between the roasting and the baking-oven; the first being provided with a special apparatus for effecting ventilation by devices more or less resembling that in Rumford’s roasting-oven. Gradually these degenerated into mere shams, and now in the best kitcheners even a pretence to ventilation is abandoned. Having reasoned out my own theory of the conditions demanded for perfect roasting some time ago (about 1860, when I lectured on ‘Household Philosophy,’ to a class of ladies at the Birmingham and Midland Institute), I have watched the gradual disappearance of these concessions to popular prejudice with some interest, as they show how practical experience has confirmed my theory, which, as already expounded, is that _fresh meat should be cooked by the action of radiant heat, projected towards it from all sides, while it is immersed in an atmosphere nearly saturated with its own vapours_.

Let it be clearly understood that I refer to the vapours as they rise from the meat, and not to the vapour of burnt dripping, which Rumford describes. The acrid properties of the products of such partial dissociation are far better understood by modern chemists than they were in Rumford’s time.

His water dripping-pan effectually prevents their formation. It is still manufactured of the precise pattern shown in the drawing, copied from Rumford’s, and cooks who understand their business at all use it as a matter of course.

The few domestic fireplace-ovens that existed in Rumford’s time were clumsily heated by raking some of the fire from the grate into a space left below the oven. Those of the best modern kitcheners are heated by flues going round them, generally starting from the top, which thus attains the highest temperature. The radiation from this does the ‘browning’ for which Rumford’s blowpipes were designed.

Here I differ from my teacher, as, according to my view of the philosophy of roasting, the browning, or the application of the highest temperature, should take place at the beginning rather than the end of the process, in order that a crust of firmly coagulated albumen may surround the joint and retain the juices of the meat. All that is necessary to obtain this effect in a sufficient degree is to raise the roasting-oven to an excessive temperature before the meat is put in. Supposing an equal fire is maintained all the while, this excessive initial temperature will presently decline, because, when the meat is in the oven, the radiant heat from its sides is intercepted by the joint and doing work upon it; heat cannot do work without a corresponding fall of temperature. While the oven is empty the radiations from each side cross the open space to reinforce the temperature of the other sides.

When I first decided to write on this subject I made some designs for kitchen thermometers intending to have them made, and to recommend their use; but was not successful. When a man condemns his own inventions, his verdict may be safely accepted without further inquiry.

I afterwards learned that Messrs. Davis & Co. had already constructed special oven thermometers, to be so attached to the oven-door that the bulb should be inside and the tube having the expansion of the mercury outside, and therefore readable without opening the door, as shown in Fig. 5, and another for standing inside the oven, Fig. 6.

I learned by these thermometers the cause of my own failure. I tried to do too much—to construct one form of thermometer to do all kinds of kitchen work. A thermometer suitable for the oven is not applicable to trying the temperature of a fat-bath used in frying. I accordingly wrote to Messrs. Davis asking them to devise a thermometer for this purpose. They have done so. It is described in the next chapter.

Is there, then, any difference at all between roasting and baking? There is. In roasting, the temperature, after the first start, is maintained about uniformly throughout; while in baking bread by the old-fashioned method, the temperature continually declines from the beginning to the end of the process; but in order that a dweller in cities, or the cook of an ordinary town household, may understand this difference, some explanation is necessary. The old-fashioned oven, such as was generally used in Rumford’s time, and is still used in country houses and by old-fashioned bakers, is an arched cavity of brick with a flat brick floor. This cavity is closed by a suitable door, which in its primitive, and perhaps its best form, was a flat tile pressed against the opening and luted round with clay. Such ovens were, and still are, heated by simply spreading on the brick floor a sufficient quantity of wood—preferably well-dried twigs; these, being lighted, raise the temperature of the arched roof to a glowing heat, and that of the floor in a somewhat lower degree. When this heating is completed (the judgement of which constitutes the chief element of skill in thus baking) the embers are carefully brushed out from the floor, the loaves, &c., inserted by means of a flat battledore with a long handle, called a ‘peel,’ and the door closed and firmly luted round, not to be opened until the operation is complete. Baked clay is an excellent radiator, and therefore the surface of bricks forming the arched roof of the oven radiates vigorously upon its contents below, which are thus heated at top by radiation from the roof, and at bottom by direct contact with the floor of the oven. The difference between the compact bottom crust, and the darker bubble-bearing top crust of an ordinary loaf is thus explained.

As the baking of a large joint of meat is a longer operation than the baking of bread, there is another reason besides that already given for the inferiority of meat when baked in a baker’s oven constructed on this principle. The slow cooling-down must tend to produce a flabbiness and insipidity similar to that of the roast meat which is served at restaurants where a joint remains ‘in cut’ for two or three hours. Of this I speak theoretically, not having had an opportunity of tasting a joint that has been cooked in a brick oven of the construction above described; but I have observed the advantage of maintaining a steady heat throughout the process of roasting (after the first higher heating above described), in the iron oven of a kitchener, or American stove, or gas oven.

Another and somewhat original method of roasting is that which is carried out in ‘Captain Warren’s Cooking Pot,’ concerning the practical result of which I hear conflicting opinions. It is a large pot containing water, inside which is suspended—like the glue chamber of a glue-pot—an inner vessel. The meat to be cooked is placed without water in this inner closed vessel, which dips into the water of the outer vessel, the steam from which is led away by a side opening or pipe. This outer water being kept boiling, the meat is surrounded only by its own vapour, in the midst of which it is cooked at a low temperature.

The result is similar to boiled meat, with the advantage of retaining those juices that pass away into the water in ordinary boiling. This advantage is unquestionable, and so far the apparatus may be safely recommended. But some of the claims made in the prospectuses that are freely distributed are questionable.

The method of roasting with Warren’s pot is to cook the meat as above described in its own vapour, then dredge with flour, and hang before the fire twenty minutes. The result is a tender imitation of roast meat, but more like boiled than roasted meat in flavour. This is much approved by many, but I am told that meat thus cooked and eaten daily palls upon the appetite. I know one, a youth (not one of our fastidious fops of the period), who, fed upon this at school during a few years, has thereby acquired a fixed aversion to boiled meat of all kinds.

Regarding the subject theoretically, it appears to me that the method recommended by Captain Warren, and followed by those who use his cooker, should be reversed for roasting; that the meat should have the twenty minutes before the fire—or in a hot oven—before, instead of after, its stewing in its own vapour. Some experiments I have made confirm this view so far as they go, but are not sufficiently numerous to settle the question.

For stewing of all kinds, and for such concoctions as Rumford’s soup (_see_ Chapter XIV.), it is an admirable apparatus, and the contrivances for carrying the steam from the outer vessel to a vegetable steamer above the cooking chamber, before described, is very ingenious and effective.

The statement in the prospectus, that the ‘nourishing juices’ otherwise wasted ‘are by that mode condensed, and form at the bottom of the vessel a rich gelatinous body,’ is misleading.

Gelatin is not volatile; the gelatinous body at the bottom of the vessel is not composed of condensed vapours, though condensed vapour of water is concerned in its formation. It is simply some of the gelatin of the joint dissolved by the water which condenses upon it, and finally drips down from the joint, carrying with it the dissolved gelatin.