Page:Popular Science Monthly Volume 57.djvu/113

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cinal preparation above mentioned is obtained in this way, and represents a fairly pure form of the diastatic principle. This bears the name of 'takadiastase.'"

Professor Agassiz's Investigations on Coral Islands.—Having steamed and observed for twenty-five hundred miles among the Paumotu Islands, Prof. Alexander Agassiz says, in a second letter from the Albatross Expedition, published in the American Journal of Science, that he has seen nothing tending to show that there has anywhere been a subsidence, but that the condition of the islands does not seem to him capable of explanation on any theory except that they have been formed in an area of elevation. All the islands examined are composed of a tertiary coralliferous limestone, which has been elevated to a greater or less extent above the level of the sea, and then planed down by atmospheric agencies and submarine erosion, and the appearance of this old rock is very different from that of the modern reef rock. In these islands the rims of the great atolls, after having been denuded to the level of the sea, are built up again from the material of their two faces, so that a kind of conglomerate, or breccia, or pudding stone, or beach rock is found on all the reef flats. On the lagoon side sand bars grow into small islands and gradually become covered with vegetation. Whenever the material supplied from both sides is very abundant the land ring becomes more or less solid; the islets become islands, separated by narrow or wider cuts, until they at length form the large islands, which seem at first to be a continuous land around the rim of the lagoon, while they are often really much dissected. In time water ceases to pass through the channels, and only the marks of them are left. Few if any of the lagoons appear to be shut off from the sea, as Dana and other writers have supposed. They simply have not boat passages. Unlike other coral regions, the Paumotu reefs seem to bear only a scanty life.

"Winking."—No satisfactory determination has been made of the reason we wink. Some suppose that the descent and return of the lid over the eye serves to sweep or wash it off; others that covering of the eye gives it a rest from the labor of vision, if only for an inappreciable instant. This view borrows some force from the fact that the record of winking is considerably used by experimental physiologists to help measure the fatigue which the eye suffers. In another line of investigation Herr S. Garten has attempted to measure the length of time occupied by the different phases of a wink. He used a specially arranged photographic apparatus, and affixed a piece of white paper to the edge of the eyelid for a mark. He found that the lid descends quickly, and rests a little at the bottom of its movement, after which it rises, but more slowly than it fell. The mean duration of the downward movement was from seventy-five to ninety-one thousandths of a second; the rest with the eye shut lasted variously, the shortest durations being fifteen hundredths of a second with one subject and seventeen hundredths with another; and the third phase of the wink, the rising of the lid, took seventeen hundredths of a second more, making the entire duration of the wink about forty hundredths, or four tenths of a second. The interruption is not long enough to interfere with distinct vision. M. V. Henri says, in L'Année Psychologique, that different persons wink differently—some often, others rarely; some in groups of ten or so at a time, when they rest a while; and others regularly, once only at a time. The movement is modified by the degree of attention. Periods of close interest, when we wink hardly at all, may be followed by a speedy making up for lost time by rapid winking when the tension is relieved.

An Ingenious Method of Locating an Obstruction.—The Engineering Record gives the following interesting account of the scientific solving of a practical commercial problem: "The pneumatic dispatch tube for the delivery of mail between the main Philadelphia post office and a branch office at Chestnut and Third Streets is a cast-iron pipe buried below the surface of the street, and in it small cylindrical carriers, six inches in diameter, are propelled from end to end by air pressure. At one time a carrier became lodged at