Page:Popular Science Monthly Volume 10.djvu/123

Rh to thirty feet, being penetrated by the frosts of the glacial epoch, and subject to the same laws of action as real glaciers.

The course of the fragments of different strata, as shales, quartz-veins, etc., can be traced down the slopes, showing unmistakably the mode of action; and the distribution of bowlders and of gold throughout this drift, though otherwise inexplicable, is readily accounted for by this hypothesis.

A Note on the Radiometer, by Prof. T. C. Mendenhall, of Columbus, Ohio, explained his method of illuminating this instrument for the purpose of projecting an enlarged image of the arms or fans upon a screen.

The radiometer being suspended vertically, a beam of light is reflected upward through it, and made to fall upon a mirror above, which, with the aid of a projecting lens, produces the image of the movable fans upon the screen. As the beam of light produces no motion when striking these fans edgewise, the most delicate experiments can be made, and their effects seen, without any disturbance caused by the light used in projection.

On cooling the Air of Buildings during Hot Weather, by Prof. Simon Newcomb, was a valuable paper, which was practical enough to satisfy those who demand that the value of all scientific labors shall be tried by the test of utility. The failure of the many plans which have been suggested for cooling buildings in summer has arisen from overlooking the fact that the human body is a "wet-bulb thermometer," and that the air needs not alone to be cooled, but to be brought to a condition which will allow speedy evaporation, and that, therefore, contrivances for simply cooling the air have not resulted in a degree of comfort at all commensurate with their trouble and expense. We have but to remember the discomfort of a moist, "muggy" day, even when the mercury marks a moderately low temperature, to see that the air needs not only to be cooled, but to be dried. It will not answer to dry the air by chemical absorption, as by sulphuric acid or lime, on account of the heat of the chemical union.

The only satisfactory way to remove the moisture is by condensation and deposition, and for the purpose of doing this effectually and economically Prof. Newcomb suggests an apparatus. He proposes, by passing the ordinary air of a summer day through an ice-chest, to reduce it to a point far below the dew-point—or, say, 35° Fahr. Thence it should be passed through a very large tin tube on its way to the outside air. Inclosing this cold-air tube, is to be another, still larger, through which warm air from the apartments is to be forced; the two streams passing in opposite directions, the readily conducting substance of the tubes facilitating the vigorous efforts of the hot and cold currents to reach an equilibrium, the moisture being, meantime, rapidly deposited on the large condensing surfaces of the tubes. The outlets of the tubes are to be together, and the resulting mixture would be a volume of dry air at a comparatively low temperature. If, for example, the air in passing through the icebox was reduced to 35°, while the air admitted to the outer tubes was at 95°, the result would be a mixture of dry air at about 70°, which, if mingled in considerable volume with the ordinary air of a room on a hot summer day, would be greatly conducive to comfort. The greatest value of Prof. Newcomb's suggestion is in utilizing the cold air on its passage for the purpose of condensing moisture. As to the quantity of ice needed to cool a given space, Prof. Newcomb was not prepared to give any exact figures., although he had made some estimates. He thought, however, that, at the price of ice in Washington, the cost of cooling the Capitol would be forty or fifty dollars per day.

Some New Points regarding the Tongue of the Picus Viridis (green woodpecker) was the title of a brief paper by Dr. Joshua Lindahl, of Sweden, in which he pointed out some errors in the common descriptions of the remarkable extension of the hyoid bones over the skull, which characterizes the woodpecker family. Having occasion to dissect the head of the green woodpecker of Sweden, he observed that the elongations of the posterior cornua of the hyoids, instead of passing