Page:Popular Science Monthly Volume 5.djvu/136

126 as a great step in advance in the method of the variation of the elements and in theoretical dynamics generally. The two sets of planetary tables are works of immense labor, embodying results only attainable by the exercise of such labor under the guidance of profound mathematical skill—and which are needed in the present state of astronomy. I trust that, imperfectly as my task is accomplished, we have done well in the award of our medal."

Nature's Distribution of Trees.—In a note presented to the Philadelphia Academy of Sciences, Mr. Thomas Meehan held it to be an error to suppose that trees are by nature placed in conditions best suited to their growth. Almost all of our swamp-trees grow much better when they are transferred to drier places, provided the land is of fair quality. He referred, among others, to sweet bay, red maple, weeping-willow, and other trees, as within his own repeated observations growing better out of swamps than in them. The reason why they originate in swamps is that their seeds can germinate only in damp places, and, of course, in the state of nature, the tree remains where the seed has germinated. Plants, as a general rule, even those known as water-plants, prefer to grow out of water, except those which grow almost entirely beneath the surface. The Taxodium distichum, in the Southern swamps, sends up "knees" from various points, often as large as old-fashioned beehives, and several feet above the surface. Not only is the cypress as large when growing in good, rather dry ground, as when growing in swamps, but the tendency to throw up these knees is in a measure lost. With the general facts before us, of the antipathy of swamp-plants to submersion, Mr. Meehan thinks it safe to conclude that these root-excrescences were the result of an effort of the plant to counteract the law which held it, so to speak, in the place of its birth.

Determination of Oxygen dissolved In Water.—At the weekly meeting of the Lyceum of Natural History on Monday, February 16th, as we learn from the Engineering and Mining Journal, Prof. Wurtz read a paper on subaërial oxidation. The author is well known to have been for some time engaged in the study of the problems connected with the water-supply of cities. Among these problems, the question of what becomes of the nitrogenous compounds contained in sewage when poured into a running stream, is one of the most important. Oxidation goes on by the action of oxygen dissolved in the water, and Prof Wurtz has long been studying the means of ascertaining the presence of oxygen in a given water, and of measuring its quantity. To do this he uses a color-test, employing for that purpose pyrogallene, which turns brown under the action of even infinitesimal quantities of oxygen. A sample of water is first made alkaline, and then a drop or two of a concentrated solution of pyrogallene in alcohol is added. If oxygen is present, the result is a brown tint; but, if an aqueous solution of pyrogallene is used, a beautiful pink is sometimes produced. With liquids containing infinitesimal quantities of oxygen, the aqueous solution of the reagent gives a pink color which gradually passes to purple and finally to brown. The depth of the color, therefore, varies with the amount of oxygen, and permits the estimation of the quantity present by the use of graduated standards.

English Fish in Indian Waters.—In December, 1867, Mr. Mclvor, Superintendent of the Chinchona Plantations, on the Nilghiri Hills, in Southern India, took out carp, tench, trout, and other fish, with which he has now stocked the rivers, streams, and lakes, of the Nilghiris. The trout have not succeeded well, but the growth and increase of the tench have been marvelous. The first English fish were put in the lake at Utakamund, in August, 1869. In 1871 and 1872 the streams flowing into the lake were well stocked with fish, and for the last few months they have been caught in large numbers by the natives, and sold in the markets. The tench greatly predominate. One interesting fact is that many European fish have been caught below the great Kalhutty water-fall, showing that they have survived after being carried down the highest fall from the Nilghiris, in the descent of the Utakamund Lake and River to the plains. It may, therefore, be expected that the rivers from the foot of the