Page:Popular Science Monthly Volume 1.djvu/525

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200 gallons. In the bottom portion of this structure are pumps for the purpose of forcing a liquid, chemically prepared, into the vessels above. The principal ingredient, besides water, is sulphate of copper. From these vessels two systems of tubing are carried downward to the ground, and continued along the surface forward to a distance of a couple of hundred yards, in a direction at right angles to the front of the rectangular structure already mentioned. Raised at slight elevation from the ground, and placed at right angles to these tubes, lie the trees to be operated upon, with their thicker ends inward; at intervals of 12 or 15 inches, in this horizontal tubing, is placed a series of taps, each connected by a short India-rubber tube to the end of a tree, to which it is secured by means of cramps and screws, and rendered water-tight by a sort of nozzle. By means of cocks at the upper end of the horizontal piping, the solution in the vats is permitted to descend. The pressure exerted from above forces it into the pipes through the India-rubber tubing and into the trees, traversing them in the direction of their fibre. In a short time, the sap and a portion of the chemical solution are seen to ooze slowly from the smaller end of the tree, when it falls into a sort of wooden gutter, inclined at such an angle as causes it to run back to a cistern near to where it had been originally prepared. After undergoing some filtration here, it is placed along with the yet unused liquid, and again performs the circuit of the vats above and trees below. The time necessary for the complete saturation of the trees varies from ten days to three weeks, according to their quality and age. In this way an application of the principles of hydrodynamics, combined with what is little more than a mechanical chemical knowledge, enables the manufacturer to provide poles for telegraphic purposes which will resist the action of the atmosphere for at least five times as long as the telegraph-poles formerly in use.


Propagation of Disease.—At a late meeting of the Manchester Philosophical Society, the president, in some remarks on the propagation of disease, pointed out how this might occur through house-drains that emptied into sewers. The sewer, acting as a reservoir, receives the diseased emanations from one house, only to send them back through improperly-trapped drains into other houses. Proof of this being a possible mode of spreading disease was furnished by a case, where, in one of the streets of a town suffering from an epidemic of small-pox, several houses on one side of the street were visited by the disease, while on the other side every house escaped. This circumstance was all the more remarkable from the fact that, on the side affected, the yards and spaces about the houses were clean and dry, while on the other side "the privies and slops overflowed the yards and lanes, and the stench was almost unbearable." On the clean side, the houses were connected with the sewer, sewage-gas was within them, and so was the epidemic. On the dirty side, none of the houses communicated with the sewer, and all were free from the disease. "Thus untrapped or badly trapped drains, terminating in sewers, may be worse than no drains at all."


Detection of Alum in Bread.—Anybody who wishes to test his bread or flour, for the presence of alum, may do so by the following process, which we find described and vouched for by Mr. John Horsley in a recent number of the Chemical News, First, make a tincture of logwood, by digesting, for eight hours, two drams of freshly-cut logwood-chips, in five ounces of methylated spirit, in a wide-mouthed phial, and filter. Second, make a saturated solution of carbonate of ammonia in distilled water. A teaspoonful of each solution mixed with a wineglassful of water, in a white-ware vessel, forms a pink-colored liquid. Bread containing alum, immersed in this liquid for five minutes or so, and then placed upon a plate to drain, will in an hour or two become blue on drying, but, if no alum is present, the pink color fades away. If, on drying, a greenish tinge appears, that is an indication of copper, as carbonate of ammonia produces that color, but never a blue.


A Singing Marmot.—Dr. Lockwood's theory of the latent singing capacity of the Rodents has received an interesting item of confirmation from an article in the June number of the American Naturalist by Dr.