Page:Popular Science Monthly Volume 6.djvu/267

Rh How Suctorial Insects feed.—It is commonly supposed that dipterous, or two-winged insects, never eat the pollen of plants, their mouths being destitute of mandibles, and fitted only with a tube, or proboscis, for sucking up juices. That this statement does not hold good for all insects belonging to this order, is shown from observations lately made by Alfred W. Bennett. This distinguished entomologist has found that at least insects of the family Syrphidæ (hoverer-flies) eat the pollen of plants. He has examined, under the microscope, the contents of the abdomen of two species of syrphidæ, which he found to be colored a bright orange, owing to the presence of enormous quantities of aster-pollen. That the grains of pollen are not accidentally taken up, but form an actual article of food, is proved by their being found in every stage of digestion, the fluid contents of the grains being apparently the nutritive substance, and the skins being ultimately excreted. During the last spring, Mr. Bennett captured Eristalis tenax (the drone-fly) on the flowers of the sloe. The abdomen of the insect was full of pollen-grains, belonging to at least three kinds of plants—sloe, dandelion, and probably fuchsia.

Oxidation retarded by Molecular Vibrations.—A paper was read, at the American Association meeting, on "Mechanical Vibration retarding Rust," by Prof. S. S. Haldeman. The iron track of a railroad is but little subject to oxidation, while iron rails piled alongside quickly rust. If traffic be suspended on a railroad for a day, and, in the mean time, a rain of some hours' duration fall on the rails, they soon show signs of rust. From these facts Prof. Haldeman argues that, in chemical combination, mechanical vibrations may interfere with the molecular arrangement of the elements. He would, however, have these casual observations submitted to the test of experiment. A discussion followed, in the course of which it was suggested that possibly the oil employed upon locomotives might be more or less spread in a thin film over rails in use, and thus prevent their oxidation. This view met with no favor. Prof. Van der Weyde was quite certain that the suggestion of Prof. Haldeman had reference to a fact in physics. Molecular vibrations do undoubtedly tend to prevent rust: a saw hung up unused would soon grow rusty, whereas if used it would keep bright; and the observation is universal with regard to mechanical tools.

The Metric System of Weights and Measures.—On the last day of the Hartford meeting of the American Association, President Barnard, of Columbia College, delivered an address on the "Metric System." He predicted that the metric system will become the sole system of weights and measures in use throughout civilized nations before the year 1900. In France, Holland, Belgium, Spain, Portugal, Italy, Switzerland, the German Empire in fact,—all Europe, except Scandinavian countries and England, and in all America, except the United States, the metric system has been adopted. Even in the Indian empire of Great Britain the metric system has been adopted, and that system has been legalized, though not yet adopted, in Great Britain and here. At the Vienna Metrological Congress, every delegate, though representing nearly every country on the civilized globe, voted for the metric system.



American Society of Civil Engineers have appointed a committee to report on plans for—1. The best means of rapid passenger transit; and, 2. The best and cheapest method of delivering, storing, and distributing goods and freight in and about the city of New York. The society ask for suggestions from all civil engineers, and others who may be possessed of any information touching the subject of their investigations. The secretary of the society is G. Leverich, and his address is 63 William Street.

December a telegram was sent from New York to London, and an answer received in 30 minutes actual time. The distances traversed were as follows: from New York to Heart's Content, N. F., 1,300 miles; cable, 2,000; Valentia to London, 300 miles. Each of the telegrams, therefore, traveled 3,600 miles, and passed through the hands of 18 persons.

international exhibition has positively been decided upon in China, and a