652 



THE POPULAR SCIENCE MONTHLY 



has some very pointed criticisms on the 

 working of the new system in England. 

 The end sought by the Government in as- 

 suming control of the telegraph interests of 

 the country was, by cheapening the rates 

 and extending the lines, to bring the advan- 

 tages of the system within the reach of a 

 larger number of people, expecting thereby, 

 just as in the case of the post-office, to de- 

 rive 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 communica- 

 tion. " Speed," says the Journal, " is the 

 very essential of the telegram ; it is its rai- 

 son d'etre ; therefore, there is no good in re- 

 ducing 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 con- 

 stitution: silex, 79 parts; water, 13; oxide 

 of iron, 3 ; alumina, 4 ; magnesium, 1. In 

 the manufacture of crystal glass and porce- 

 lain this discovery is of considerable inter- 

 est, 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 prepar- 

 ing 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 ex- 

 cludes damp. 



White Spots on Photograph Proofs. 



Ever since the invention of photography on 

 paper, says the Monileur Scientifiqne, pho- 

 tographers have been trying to discover the 

 cause of those white points which so fre- 

 quently 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 hypochlo- 

 rite of soda, used by the paper-maker for 

 bleaching purposes. But, as the manufac- 

 turers 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, where- 

 as 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 re- 

 sult was, that at first a yellow point, which 

 soon turned to brown, appeared in the cen- 

 tre of the spots, finally extending over their 

 entire surface. Hence, the author con- 

 cludes 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 



