SCIENTIFIC SUMMARY. 
387 
blue. May not, we suggest, the oxide, — which must not be crystalline, but in 
the amorphous state, — have a common principle of action with spongy platinum 
and charcoal, and other non-magnetic porous bodies ? But whatever be the 
theory of its action, its effects in removing oxidizable and other organic 
matter from water are undoubted. — Yide Medical Times and Gazette, April. 
The Absorption-lines of the Didymium Spectrum. — At a late meeting of the 
Manchester Philosophical Society, Professor Roscoe stated that he had re- 
ceived a letter from Professor Bunsen, announcing the discovery of a most 
interesting and important fact, namely, that the well-known black absorption- 
lines of the Didymium spectrum when examined with polarized light vary 
according to the direction in which the light is allowed to pass through the 
crystal. This shows that the position of the black absorption -lines is in some 
degree dependent upon the physical structure of the body through which the 
light passes, and is not merely determined by its chemical constitution. — 
Yide Proceedings of Philosophical Society. 
An Explosive Paper, which is intended to be a substitute for gunpowder, 
has been invented by Mr. G. S. Melland, of Lime Street, London. The Artizan , 
which devotes an article to the subject, states that it is paper impregnated 
with a composition formed of chlorate of potash, 9 parts ; nitrate of potash, 
44 ; prussiate of potash, 3^ ; powdered charcoal, 3^ ; starch, X V part ; chro- 
mate of potash, X V part ; and water, 79 parts. These are mixed and boiled 
during one hour. The solution is then ready for use, and the paper passed in 
sheets through the solution. The saturated paper is now ready for manu- 
facturing into the form of a cartridge, and is rolled into compact lengths of 
any required diameter. These rolls may also be made of required lengths, 
and cut up afterwards to suit the charge. After rolling, the gun-paper is dried 
at 212° F. ; and has the appearance of a compact greyish mass. Experiments 
have been made with it, and it has been reported favourably of, as a perfect 
substitute for gunpowder, superseding gun-cotton and all other explosives. 
It is said to be safe alike in manufacture and hi use. The paper is dried at a 
very low temperature. It may be freely handled without fear of explosion, 
which is not produced even by percussion. It is, in fact, only exploded by 
contact with fire, or at equivalent temperatures. In its action, it is quick 
and powerful, having, in this respect, a decided advantage over gunpowder. 
Its use is unaccompanied by the greasy residuum always observable in gun- 
barrels that have been fired with gunpowder. Its explosion produces less smoke 
than from gunpowder ; it is said to give less recoil, and it is less liable to de- 
terioration from dampness. It is readily protected from all chance of damp, 
by a solution of xyloidm in acetic acid. The xyloidin is prepared by acting 
on paper with nitric acid, one part thereof being dissolved in three parts of 
acetic acid of specific gravity of 1'040. 
The Formation of Ice at great Depths. — An interesting instance of this 
phenomenon has recently been recorded by the Detroit Water Commissioners, 
who have for a long time (some years) met with difficulties hi obtaining 
water from the river during winter : — The inlet pipe extends into the river 
for a distance of 150 feet, and on the end, which is bell-shaped and turned 
upwards, there is a horizontal strainer pierced with half-inch holes. When 
the river is covered with ice over the strainer, the ice does not collect at any 
degree of cold, but the greatest difficulty recurs when the thermometer ranges 
