Page:Popular Science Monthly Volume 26.djvu/844

844 may he looked upon as supplying the source of power. The one may be spoken of as holding the position of the instrument of action, while the other supplies the motive power. Nitrogenous alimentary-matter may, it is true, by oxidation, contribute to the generation of the moving force, but, as has been explained, in fulfilling this office there is 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 utilized in force-production."

The italics are mine, for reasons presently to be explained. The following pages of Pavy's work contain repetitions and 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, etc., viz., a little tubular furnace charged with a mixture of the combustible to be tested, and chlorate of potash (better a mixture of chlorate and nitrate). 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.

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:

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), beef-fat having nearly eight times the value of lean beef. Ten grains of rice give 7,454 foot-pounds of working power, while the same quantity of lean beef only 2,829; according to which one pound of rice should supply as much support to hard workers as two and one half pounds of beefsteak. None of the modern theorists dare to be consistent when dealing with such direct practical applications.