Page:Popular Science Monthly Volume 3.djvu/136

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panies, we are told by Mr. James E. Whitney, in the Railway Times, that, of a lot of axles furnished to the Mobile & Ohio Railroad Company, but one-fourth were capable of meeting the required test, and the other three-fourths were returned to the manufacturer. Mr. Whitney also says that the duty of making these tests belongs to the railway companies themselves, which leaves them no valid excuse for the employment of defective materials.

Besides the use of poor iron, the resisting power of the axle may also be lessened by the method of manufacture. "The ideal axle," says Mr. Whitney, "would have its metal as dense as possible, and hence would be shaped mainly by hammering. Its fibres would run unbroken throughout its length, and the tough outer skin, which in wrought as in cast iron is much stronger than that within, would be preserved in its integrity." As now manufactured, a portion of this is removed by turning, and the axle proportionally weakened. The turning process is also carried to the formation of sharp corners, which, as shown by Rankin, eventually become the starting-points of annular or circumferential grooves that continue to deepen until the central portion is too much diminished to bear the shock of the unusual jar: "The ordinary 'tapping' will, in aggravated cases, enable such a flaw to be detected, but no skill and no care will guard against the slow but sure approach of danger, because of the unnecessary removal of a few annular chips at the shoulder of the wheel-bearing, to gratify the whim of the turner."

But, however strong originally, car-axles always deteriorate with use, the constant succession of jars to which they are subject gradually impairing the strength of the iron. The character of this change is not well understood, and the only effective method now known, of guarding against the danger arising from it, is to throw the axle aside after it has been run a certain number of miles.

Bowlder-like Masses of Clay in Drift.—Masses of stratified gravel, similar in shape to the clay-bowlders mentioned in the March number of this monthly as occurring in the drift of Long Island, were found during the excavation of the Chicago Tunnel in the drift under Lake Michigan. In the American Journal of Science for January, 1867, Prof. E. Andrews thus describes them: "They lay in all imaginable positions, sometimes with their strata set up at high angles. They were from a few inches to a few feet in diameter, and were embedded in the solid, impervious clay nearly 80 feet below the surface of the lake. The gravel was water-worn, and often so clean that it would scarcely soil a handkerchief. The interstices commonly contained a few gallons of water in the lower part, and some air or gas in the upper. The gas was in many instances inflammable. The pockets scarcely leaked a drop when once emptied, and the cavities looked exactly, in many instances, like casts of rounded bowlders."

Prof. Andrews believes they were deposited as frozen masses which thawed after they were embedded in the clay. This view is corroborated by an experiment made two years ago by Mr. E. Lewis, of Brooklyn. During a period of cold weather he selected an inlet of the sea through which the tidal flow was rapid, and in which the water was several degrees below freezing. The bottom was frozen where the water was 10 feet deep, but there was no ice on the surface. A mass of frozen earth weighing about 50 pounds was sunk, by means of a cord, at the deepest part of the inlet. Six days afterward this mass was unchanged, except that its extreme surface was slightly soft and moist. At the expiration of 30 days it was again examined, and found to be somewhat wasted. The temperature of the water was then 3° above freezing. "If," says Mr. Lewis, "this mass had been covered by a quantity of sand or gravel, thrown down upon it while frozen, it would have retained its form; and enormous masses of such material are sometimes deposited suddenly from floating ice and glaciers."

Marked Case of Heredity in Mastiffs.—Mr. Darwin communicates to Nature a letter from Mr. Huggins on the hereditary transmission, in a breed of mastiffs, of a strong antipathy to butchers and butchers' shops. Mr. Huggins owns a dog, "Kepler," whose sire was a celebrated mastiff, "Turk." When "Kepler" was six months old he fol-