Page:Popular Science Monthly Volume 10.djvu/264

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to make. Cultivated trees had grown so much faster than was expected that people had been surprised at the growth, and it was now becoming generally known that wood came into profit much sooner than was thought possible years ago, and forest culture was much more popular in consequence. In his State at least 80,000 acres of timber had been planted during the past few years, and the work was still going on. He gave figures as to the growth of individual species, chiefly from facts within his own observation. Mr. Meehan, from whose Gardener's Monthly we take this account of the meeting, thought that the people, without government interference, can be safely trusted with the care of our forests, and the work of reforestation. Individual effort, encouraged by State laws and agricultural and horticultural societies, would soon replace the decaying forests of our land.


How the Menopoma casts its Skin.—Since reading his "Preliminary Note on the Menoponia Alleghaniense of Harlan," before the American Association, Grote has observed in the aquarium of the Buffalo Society of Natural Sciences the process by which the menopoma rids itself of its outer skin. This thin and transparent membrane is first seen to loosen and separate from the entire surface of the body, appearing at this stage like an envelope or glove in which the animal is contained. By a number of wide gapings, during which the mouth is opened to the fullest extent, the skin is parted about the lips, and then commences to fold backward from the head. Convulsive and undulating movements with the body and fore-legs are employed to extract these from the loose skin. The skin then readily falls backward, as the animal crawls forward and out of it, until the hind-legs are reached, when the menopoma turns round upon itself, and, taking the skin in its mouth, pulls it over the legs and tail. The operation reminds one of taking off clothes. The cast-off skin is retained in the mouth and finally swallowed. The operation is quickly performed.


Poisonous Cooking-Utensils.—The danger attending the use of porcelain-lined cooking-vessels was pointed out at a meeting of the British Society of Public Analysts, by Mr. Robert R. Tatlock. He stated that the milk-white porcelain enamel with which cast iron cooking-vessels are now so commonly coated is in the highest degree objectionable, on account of the easy action on it of acid fruits, common salt, and other substances, by means of which lead and even arsenic are dissolved out in large quantity during the process of cooking. It was shown that it is not so much on account of the presence of large proportions of lead and arsenic that these enamels are dangerous, but because they are so highly basic in their character, and are so readily acted on by feebly-acid solutions. He thought that no enamel should be admitted to use unless it was totally unaffected by boiling with a one-per-cent. solution of citric acid, which was a very moderate test. Further, he gave it as his opinion that either the use of such poisonous ingredients as lead and arsenic in large quantity should be entirely discontinued, or that the composition otherwise should be of such a character as to insure that none of the poisonous substances could be dissolved out under ordinary circumstances.


Agencies that formed the Colorado Cañons.—The great cañon of the Colorado is from 3,000 to 6,000 feet deep, through a distance of 200 miles. All the side-streams reach it through profound canons, and each stream has done, and is still doing, its own work of erosion. The process by which these results are brought about is considered by Prof. G. R, Gilbert, in the American Journal of Science and Arts, under three principal heads: 1. Weathering; 2. Transportation; 3. Corrasion.

By weathering, the writer means the disintegration of rock by the action of temperature—beating of rain and changes of vegetation. The process, however, would be greatly delayed if the loosened material was allowed to remain and cover the surface. Hence transportation becomes a powerful agent in erosion, not only by exposing the disintegrating surfaces, but by mechanical wear in the act of removal.

All rocks are more or less soluble in water, and impurities in the water intensify solvent action. But it usually happens that