Page:Popular Science Monthly Volume 49.djvu/589

Rh equipment for that struggle. If we compare as best we may with our limited information the general characteristics of the high-fed and low-fed classes and races, there is, I think, to be perceived a broad distinction between them. In regard to bodily strength and longevity the difference is inconsiderable, but in regard to mental qualities the distinction is marked. The high-fed classes and races display, on the whole, a richer vitality, more momentum and individuality of character, and a greater brain power than their low-fed brethren; and they constitute the soil or breeding ground out of which eminent men chiefly arise.' It is well understood that differences in mental capacity may be explained, in part at least, by differences in the type of nutrition of the brain cells, and nutrition is unquestionably modified and influenced by the quality of the food consumed. To again quote Sir William Roberts: 'Trainers will tell you that the hunter and the draught horse require to be fed differently. In the hunter is wanted rapid liberation of energy within a comparatively short space of time; in the draught horse is wanted a more gradual liberation of energy and for a longer period. The hunter is fed on a concentrated and stimulating food, the heaviest and most expensive oats, which, if I may so express it, is the beef of the vegetable feeders, while the draught horse is fed on a lower and less stimulating diet—on Indian corn and chopped hay, food which tends to increase bulk and weight.' So with mankind, the nature and quality of the nutrient—aside from its containing the due proportion of the several requisite elements—exert a specific influence upon the character of mind and body; and meats may be fairly placed in the front rank of foods as giving important aid toward that higher physical and mental development which belongs to the civilization of the nineteenth century."

Uranium.—Until the introduction of the electric furnace by M. H. Moissan, the oxides of many of the metals had been looked upon as irreducible by carbon. M. Moissan, three years ago, isolated the metal uranium in this way. The metal, when pure, is perfectly white, and is not magnetic. It has the remarkable property of emitting invisible phosphorescent rays capable of producing photographic effects through a medium opaque to ordinary light vibrations. The effects are precisely similar to those previously obtained from uranium salts, except that they are nearly four times as intense. The chemical behavior of uranium depends to a certain extent upon its state of division. The metal obtained by electrolysis, which is finely divided, takes fire in fluorine, is attacked by chlorine at 180°, by bromine at 210°, and by iodine at 260°, the reaction in all cases being complete. The powdered metal is completely burned in pure oxygen at 170°, and decomposes water slowly at the ordinary temperature, but more quickly at 100°. Uranium is one of the rapidly increasing group of metals which combine directly with nitrogen at high temperatures, and hence in its preparation it is necessary to work in such a manner as to completely exclude the air.

Working in Compressed Air.—E. W. Moir, in a paper read before a recent meeting of the Society of Arts, gave some interesting data regarding the effects upon the human system of working in compressed air and the various practical means of lessening the danger and overcoming any sudden collapses. Mr. Moir had charge of the work on the Hudson River Tunnel for a time, and has had some connection with most of the underground tunneling ventures of the past two decades. He says: "When I first came to New York the men had been dying at the rate of one man per month out of forty-five or fifty men employed, a death-rate of about twenty-five per cent per annum. With a view to improving this state of things, an air compartment like a boiler was made, in which the men could be treated homœopathically, or reimmersed in compressed air. It was erected near the top of the shaft, and when a man was overcome or paralyzed, as I have seen them often, completely unconscious and unable to use their limbs, they were carried into the compartment, and the air pressure raised to about one half or two thirds of that in which they had been working, with immediate improvement. The pressure was then lowered at the very slow rate of one pound per minute, or even less, the time allowed for equalization being from twenty-five to thirty minutes, and, even in severe cases, the men went away quite cured. No man ever suffers