Page:Popular Science Monthly Volume 2.djvu/652

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has some very pointed criticisms on the working of the new system in England. The end sought by the Government in assuming control of the telegraph interests of the country was, by cheapening the rates and extending the lines, to bring the advantages of the system within the reach of a larger number of people, expecting thereby, just as in the case of the post-office, to derive sufficient income for the maintenance of the lines by the increased patronage that cheap rates would secure. As was anticipated, a large increase of business has resulted; but this very increase promises to defeat the chief advantage which the telegraph is designed to afford, viz., speed of communication. "Speed," says the Journal, "is the very essential of the telegram; it is its raison d'être; therefore, there is no good in reducing the charge for this convenience, if the convenience itself vanishes. It becomes, in fact, much more expensive. We now pay a shilling for a telegram, when a penny stamp, or even a half-penny card, would have sufficed. In former days a telegram was an outlay, certainly, but we paid much for a speed that we obtained. Many would still pay as much for the same advantage, but find they pay a reduction for a ghost of it." The writer does not despair of a remedy for this state of things, but says that the reticence of the authorities concerning the details of their management prevents the suggestion of any means of relief. The case adds one more to the already long list of examples where the Government plays the part of an obstructive.

Silica as a Basis of Paint.—There was lately discovered in North Wales a deposit of almost pure silica, several feet in depth, which on analysis shows the following constitution: silex, 79 parts; water, 13; oxide of iron, 3; alumina, 4; magnesium, 1. In the manufacture of crystal glass and porcelain this discovery is of considerable interest, but it is perhaps still more valuable as furnishing an excellent fire-proof and water-proof paint. When taken from the bed the silica is freely washed in water, and on being dried it becomes brilliantly white, and is then an impalpable powder. In preparing it as a base for paint, the water is dried out. It mixes readily with pigments and oils, is worked with the greatest ease, and resists the action of acids and of heat. When perfectly dry, the paint is extremely hard and polished on the surface. Applied on the inside or outside of houses, it excludes damp.

White Spots on Photograph Proofs.—Ever since the invention of photography on paper, says the Moniteur Scientifique, photographers have been trying to discover the cause of those white points which so frequently appear on their proofs, destroying their value as works of art, and rendering them unsalable. It is commonly supposed that these spots are owing to a defect in the paper—the presence in it of hypochlorite of soda, used by the paper-maker for bleaching purposes. But, as the manufacturers claim that chemical analysis fails to detect in their goods the faintest trace of the hypochlorite, M. Ernest Baudrimont set himself to discover where the fault lay. He first made a thorough analysis of the paper and the size used in taking photographs, but without finding there the cause of the spots. One thing, however, he did discover, which helped him to find the true solution of the problem, and this was that the spots always occurred on the face of the picture, but never on the back. He next artificially produced some spots on a perfect proof, by the employment of the hypochlorite of soda, the hyposulphite of soda, and the cyanide of potassium. After drying the pictures, he applied to the spots a solution of nitrate of silver. It was found that the white spots produced by the hypochlorite and by the cyanide remained totally unchanged, whereas those produced by the hyposulphite very rapidly changed, first to a yellow, then to a brownish tint. M. Baudrimont next touched with the silver solution spots appearing spontaneously on some pictures, and the result was, that at first a yellow point, which soon turned to brown, appeared in the centre of the spots, finally extending over their entire surface. Hence, the author concludes that the white spots occurring in photograph proofs are entirely owing 10 the hyposulphite of soda, used to fix the positive impression. If the proof is not thoroughly washed after the application of the hyposulphite, or if it is dried between