The results of these experiments show, in a striking manner, how important it is to the saving of fuel in baking bread, to keep the oven continually going, without ever letting it cool: for in the first experiment when the oven was cold, when it was begun to be heated, the quantity of wood required to heat it was 366 1/2 lbs.; but in the sixth experiment, after the oven had been well warmed in the preceding experiments, the quantity of fuel required was only 74 1/2 lbs.
As in these experiments 2393 lbs. 13 loths of bread were baked with the heat generated in the combustion of 880 lbs. of wood, this gives to each pound of bread 11 1/3 loths, or 34/96 of a pound, of wood.
In the fifth experiment, or batch, 186 loaves weighing (at 2 lbs. 5 1/2 loths each) 304 lbs. were baked, and only 80 lbs. of wood consumed, which gives but a trifle more than 1/4 of a pound of wood to each pound of bread; or 1 pound of wood to 4 pounds of bread.
As each loaf weighed 2 lbs. 16 loths when it was put into the oven, and only 2 lbs. 5 1/2 loths when it came out of it, the loss of weight each loaf sustained in being baked was 10 1/2 loths, as has already been observed. Now this loss of weight could only arise from the evaporation of the superabundant water existing in the dough; and as it is known how much heat, and consequently HOW MUCH FUEL is required to reduce any given quantity of water, at any given temperature, to steam, it is possible, from these data, to determine how much fuel would be required to bake any given quantity of bread, upon the supposition that NO PART OF THE HEAT GENERATED IN THE COMBUSTION OF THE FUEL WAS LOST, either in heating the apparatus, or in any other way; but that the whole of it was employed in baking the bread, and in that process alone. And though these computations will not show how the heat which is lost might be saved, yet, as they ascertain what the amount of this loss really is in any given case, they enable us to determine, with a considerable degree of precision, not only the relative merit of different arrangements for economizing fuel in the process of baking, but they show also, at the sane time, the precise distance of each from that point of perfection, where any farther improvements would be impossible: And on that account, these computations are certainly interesting.
In computing how much heat is NECESSARY to bake any given quantity of bread, it will tend much to simplify the investigation, if we consider the loaf as being first heated to the temperature of boiling water, and then baked in consequence of its redundant water being sent off from it in steam.
But as the dough is composed of two different substances, viz. rye meal and water, and as these substances have been found by experiment to contain different quantities of absolute heat; or, in other words, to require different quantities of heat, to heat equal quantities or weights of them to any given temperature, or any given number of degrees, it will be necessary to determine how much of each of the ingredients is employed in forming any given quantity of dough.
Now, in the foregoing experiments, as 1102 loaves of bread were formed of 1736 lbs. of rye meal, it appears, that there must have been 1.47 lb. of the meal in each loaf; and as these loaves weighed 2 1/2 lbs. each when they were put into the oven, each of them must, in a state of dough, have been composed of 1.47 lb. of rye meal, and 1.03 lb. of water.
Supposing these loaves to have been at the temperature of 55 degrees of Fahrenheit's Thermometer when they were put into the oven, the heat necessary to heat one of them to the temperature of 212 degrees, or the point of boiling water, may be thus computed.