Page:Popular Science Monthly Volume 4.djvu/134

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is dried. When it is left to itself to dry, it becomes shriveled, and has a bad appearance. To guard against this, the following process is adopted: An endless strip of paper is passed by machinery first through a vat of sulphuric acid, and then through water, ammonia, and water again; next a cloth-covered roller deprives it of a portion of the water, and finally it is pressed and smoothed out by means of polished heated cylinders.

When properly manufactured, parchment-paper has the same color and translucency as animal parchment, its structure having undergone a change from fibrous to corneous. In point of cohesion and hygroscopicity, it is very much like common parchment. When dipped in water, it becomes soft and flaccid. It is impermeable to liquids, except by dialysis. These qualities render parchment-paper specially suitable for diplomas, important papers, and in general for documents which it is desirable to preserve. As compared with ordinary parchment, this paper possesses the advantage that it is very little liable to be attacked by insects. Then, too, the characters inscribed on it cannot be effaced without difficulty, and, when effaced, cannot be replaced by others—a perfect guarantee against all kinds of falsification. By reason of its firmness and durability, it is specially suited for plans and drawings, particularly architectural drawings, which are much exposed to moisture. Further, it might be used for covering books; or books, maps, etc., for use in schools, could be printed on it, and would be very durable. In place of animal membrane, it is well suited for covering jars of fruit, extracts, etc., as also for connecting the parts of distilling and other apparatus. It furnishes excellent casings for sausages. In surgery it is employed instead of linen, oiled cloth, and gutta-percha, for dressing wounds.

Improvements In Street-Sprinkling.—An improved method of sprinkling streets has been patented in England, by means of which almost five-sixths of the expense of watering may be saved. It appears that the cost for labor in watering the streets of London averages about $675,000 per annum, the cost of water being additional; and it is contended that this work can be done in a far more effectual and advantageous manner, by a system of permanent pipes, for an expenditure of less than $15,000 per annum, while the interest upon the plan necessary for the purpose would not exceed $100,000. An experiment made in Hyde Park warrants the conclusion that, with the permanent system referred to, the services of one man would be amply sufficient for laying the dust over the whole of the drives and rides in that park—a task which at present engages twenty men, with as many horses and carts. This area may be taken as a seventy-fifth part of the total road-way in London to be watered; and hence we may conclude that about seventy-five men, without either horses or carts, could water the whole metropolis at the cost for labor above stated. The city government of London is giving the matter serious consideration; and, if water is to continue in use for the purpose of laying dust on thoroughfares, the plan will doubtless be generally adopted on being proved practicable. It is to be hoped, however, that before long deliquescent salts will be employed for this purpose rather than water. The use of water in summer hastens the decay of organic matter, and thus is objectionable from a sanitary point of view. Deliquescent salts will not alone lay the dust, but will also disinfect the streets by checking decomposition.

French Association for the Advancement of Science.—The French Association met at Lyons, on August 21st, the opening address being made by the president, Quatrefages. He traced the history of scientific progress during the past hundred years, and advocated the claims of science as an important branch of general education. The reports of the secretary and treasurer show that the Association is in a flourishing state, and that it has already, in its second year, commenced to give material encouragement to original investigators of science. The most notable of the papers read in the general meetings were the following: Dr. H. Blanc, Surgeon-Major of the British Army, on "The Means of guarding against Cholera: an Essay based on Practical Knowledge of the Causes and Mode of Propaga-