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Page:Popular Science Monthly Volume 56.djvu/749

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733
FRAGMENTS OF SCIENCE.

could be bought for twenty-five cents an acre in large tracts, but it now brings from two dollars to five dollars Mexican. These lands can be used for other crops while the trees are growing up, and thus made partly to repay the cost of starting the plantation. So the expense of clearing the land preparatory to planting it is largely met, if facilities for transplantation are at hand, by the sale of the dyewoods, sandalwood, satinwood, ebony, and mahogany that are cut off. The land should be chosen along the banks of streams, where the soil is rich, deep, and loamy, and the presence of wild rubber trees is a sure indication of its suitability. These wild trees should be left standing, and young seedlings should be kept and transplanted into their proper places. The densest plantation compatible with good results is fifteen feet apart, giving about one hundred and ninety-three trees to the acre. Once in the ground, the tree needs no attention or cultivation beyond keeping down the undergrowth, which can be effected by the aid of a side crop. The tree propagates itself by the seeds or nuts, which drop in May and June. By the sixth or seventh year the grove will be in bearing, and thereafter should yield from three to five pounds of India rubber per tree.

 

The New York Botanical Garden's Museum.—The museum building of the New York Botanical Garden is substantially completed, and most of the works are in an advanced state of forwardness. The museum cases (for public inspection) and the herbarium cases (for students) are in position, and the herbarium cases are filled. Among the recent gifts of value to the institution are the miscellaneous collection of John J. Crooke, made about thirty years ago and containing about twenty thousand specimens, among which are a set of the plants obtained by the United States Pacific Exploring Expedition of about 1850; the collection of between twenty and thirty thousand specimens made by Dr. F. M. Hexamer in Switzerland and the United States; a collection of seven or eight thousand numbers, made by Mr. and Mrs. A. A. Heller, representing between twelve and thirteen hundred species, some of which are new to science; and specimens of crude drugs, for the Economic Museum, presented by Parke, Davis & Co. A permanent microscopic exhibition is to be established by Mr. William E. Dodge, at his own expense. It will be furnished with at least twenty-five microscopes, and with specimens carefully prepared and inclosed, to secure them from injury. A set of more than two hundred volumes on botany and horticulture, which formed a part of the library of Dr. David Hosack, founder of the first botanical garden in New York, has been presented by the New York Academy of Medicine, which received it from the New York Hospital.

 

Action of Sea Water on Cements.—As the result of examinations of many masonry structures immersed in sea water. Dr. Wilhelm Michaelis has found that Portland cement does not resist the chemical action of such water so well as do Roman cement and the hydraulic cements. The soluble sulphates in the sea water appear to enter into a substitution combination with the lime which exists in the cement in a free state or is liberated in the hardening, and it is converted into a sulphate, while disintegration ensues. In Roman cement the lime exists in combination, and there is no inclination toward the formation of a sulphate, and hydraulic limes resemble Roman cement in physical qualities. Dr. Michaelis suggests that hydraulic cementing materials containing more lime than is required for the formation of stable hydro-silicate and aluminate may be made suitable for submarine work by an admixture of trass or puzzolana, whereby the cementing strength of the mass will be greatly increased, and it will be enabled to withstand the disintegrating action of the sea water.

 

Stories of Amazonian Pygmies.—Dr. D. G. Brinton subjected the stories of the existence of pygmy tribes on the upper tributaries of the Amazon to a careful examination, and came to the conclusion that the facts did not show anything more than that there are undersized tribes in that part of South America, with occasional individual examples of dwarfs, such as occur in all communities. It is still a question, he observed, "whether the rumor of a pygmy people somewhere in the tropical for-