Page:Popular Science Monthly Volume 5.djvu/232

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THE POPULAR SCIENCE MONTHLY.

provement can be expected from other means than from skillful and judicious moral intervention on the physician's part.—Revue des Deux Mondes.

Note, by the Editor of the Revue.—Circumstances have prevented the earlier publication of the foregoing sketch, which has been for some time in our possession. It is the last one sent us by one of our most sympathetic fellow-laborers, whom death removed suddenly and prematurely from his friends, the 2d of January, at the age of twenty-six.

 

THE ATMOSPHERE AS AN ANVIL.[1]
By Professor J. P. COOKE, Jr.

THE office of the atmosphere, as an anvil upon which rocks are shattered for the protection of humanity, has sufficient novelty about it to require explanation. It has come to be pretty well understood now that rocky fragments of all sizes are flying through space, like the planets themselves. What the effect would be, if hard meteoric stones were to strike, with a velocity sixty times as great as that of a cannon-ball, the structures that man builds upon earth, it is not difficult to imagine. To say nothing of the larger stones, no ordinary buildings could afford shelter from the smallest particles striking with the velocity of eighteen miles per second. Even dust flying at such a rate would kill any animal exposed to it. How effectually we are guarded by the atmosphere, as with a shield, impenetrable in proportion to the violence of the assaults upon it, is admirably illustrated by Prof. Cooke in the following statement, condensed from Chapter X. of his "New Chemistry:"

"Within a few years our community have become familiar with the name and terrible effects of a new explosive agent, called nitro-glycerine, and I feel sure that you will be glad to be made acquainted with the remarkable qualities and relations of this truly wonderful, substance. Every one knows that clear, oily, and sweet-tasting liquid called glycerine, and probably most of you have eaten it for honey. But it has a great many valuable uses, which may reconcile you to its abuse for adulterating honey, and it is obtained in large quantities, as a secondary product of the manufacture of soap and candles, from our common fats. Now, nitro-glycerine bears the same relation to glycerine that saltpetre bears to caustic potash. Common saltpetre, which is the oxygenated ingredient of gunpowder, is called in chemistry potassic nitrate, and, although the commercial supply comes wholly from natural sources, it can easily be made by the action of nitric acid on

  1. Condensed from "The New Chemistry," Chapter X., "Gunpowder and Nitro-Glycerine"