Page:Popular Science Monthly Volume 33.djvu/732

714 as "gorgets" and "banner-stones," were applied. By the aid of a committee of ladies of Boston, the famous "Serpent Mound" in Adams County, Ohio, has been bought, with about sixty acres of land, put in order, inclosed, and made the central object of an attractive park. "The example," says Curator Putnam, in his report, "thus set for the preservation of the ancient works of this country, has already aroused others to action, and many individuals and societies, particularly in Ohio, are now urging immediate action to prevent the further destruction of our archæologic monuments in the States."

Origin of Lake Superior Iron-Ore.—R. D. Irving, studying the ferruginous schists and iron-ores of the Lake Superior region, has found both of the theories that have been put forward to account for them—that of an eruptive, and that of a sedimentary origin—inadequate. He proposes a new theory, that the rocks have been derived from original carbonates by a metastomic process, or by replacement of the original dolomitic or calcitic rock by siliceous and ferruginous substances. The various steps by which this process took place may have been as follow: 1. The original form of the beds was that of a series of thinly-bedded carbonates, interstratified with carbonaceous shaly layers, which were also often impregnated by the same carbonate. This carbonate was generally more or less highly ferriferous, though probably there were intermediate forms between it and dolomite. 2. By a process of silicification—which varied in degree—these carbonate-bearing layers were transferred into the various kinds of ferruginous rocks now met with in the region. 3. The iron thus removed from the rock at the time of silicification passed into solution in the percolating waters, to be redeposited in various places as it became further oxidized, thus making ore bodies and various impregnations. 4. In other places, instead of leaching it out more or less completely, the silicifying waters seem to have decomposed the iron carbonate in place, producing a magnesia silicate, or a magnesia iron silicate, the excess of iron oxidizing imperfectly, and separating out as magnetite, and the excess of silica crystallizing finally as a minutely interlocked quartz ground mass. 5. The bodies of rich ore have probably had different origins in different cases. 6. Some of the silicifying process went on before the folding of the formations; but some also afterward. It is not supposed that this theory will not require modification in the future, but it is the one to which the author has been led, without being influenced by any preconceived notions, very gradually, during the growth of his experience with the minerals of the region.

How long one can remain under Water.—The length of the time during which a person can remain under water without choking—a subject on which exaggerated stories have been told—has been studied by M. Lacassagne. The author was favored with an opportunity to examine Captain James, a celebrated diver, whose exploits have excelled those of all his rivals. He pretended to be able to continue four minutes and fourteen seconds under water. He contended once in England for a prize which was offered to any person who could endure five minutes, but was compelled by a hæmorrhage of the nose and ears to rise at the end of four minutes. He had also swum under water during the same time a distance of one hundred and fifty metres. He was accustomed before plunging to expel all the air from his lungs and take a strong inspiration. In the water he swallowed on the average about a litre of the liquid. When he came out of the water he snorted enormously. In one of the experiments to which M. Lacassagne subjected him, the movements of the heart became slow, irregular, and feeble at the end of two minutes; and on his coming out at the end of two minutes and thirty-seven seconds, his face was congested and his eyes flushed. Important facts in the experiments were that in his full inspirations previous to plunging Mr. James swallowed air, and while under the water a considerable quantity of saliva; and that his respiratory movements did not cease during immersion, but continued ample and regular at the rate of twenty a minute, while the thoraco-abdominal cavity diminished at a gradual and regular rate. M. Lacassagne explains these circumstances by supposing that inspiration under water draws into the lung the air contained in the pharynx, which