The Chemistry of Cookery

evidence before us to show that it is split up into two distinct portions, one containing _the nitrogen, which is eliminated as useless, and a residuary non-nitrogenous portion which is retained and utilised in force-production_.’ The italics are mine, for reasons presently to be explained. Pavy’s work contains repetitions and further illustrations of this attribution of the origin of force to the non-nitrogenous elements of food. Then we have a statement of the experiments of Joule on the mechanical equivalent of heat, connected with experiments of Frankland with the apparatus that is used for determining the calorific value of coal, &c.—viz. a little tubular furnace charged with a mixture of the combustible to be tested, and chlorate of potash. This being placed in a tube, open below, and thrust under water, is fired, and gives out all its heat to the surrounding liquid, the rise of temperature of which measures the calorific value of the substance (see fig. 7, page 21, ‘Simple Treatise on Heat’). From this result is calculated the mechanical work obtainable from a given quantity of different food materials. That from a gramme is given as follows: Beef fat 27,778 } Units of work, Starch (arrowroot) 11,983 } or number of Lump sugar 10,254 } pounds lifted Grape sugar 10,038 } one foot. In Dr. Edward Smith’s treatise on ‘Food,’ the foot-pound equivalent of each kind of food is specifically stated in such a manner as to lead the student to conclude that this represents its actual working efficiency _as food_. Other modern writers represent it in like manner. Here, then, comes the bearing of these theories on my subject. A practical dietary or _menu_ is demanded, say, for navvies or for athletes in full work; another for sedentary people doing little work of any kind. According to the new theory, the best possible food for the first class is fat, butter being superior to lean beef in the proportion of 14,421 to 2,829 (Smith), and beef fat having nearly eight times the value of lean beef. Ten grains of rice give 7,454 foot-pounds of working-power, while