360 Miscellancous. 
This point is worth remembering—that theoretically we 
should have a horse-power from two-elevenths of a pound 
of coal perhour. ‘The very best engines give a horse-power 
from about two pounds of coal per hour, and it is a good 
engine that produces a horse-power from four pounds of 
coal per hour. An engine that gives a horse-power with 
two pounds of coal per hour utilizes in work about nine per 
cént. of the whole power of the coal; and one that yields a 
horse-power for four pounds of coal per hour, utilizes about 
four and a half per cent. of the power of the coal. 
PHOTOGRAPHING UNDER THE SEA.—M. Bazin, favour- 
ably known for his photographic researches, has contrived 
a very ingenious submarine photographic studio, by which 
he is enabled to take photographs of sunken ships, rocks, &c. 
The chamber is provided with lens-shaped water-tight win- 
dows, and by means of the electric light the objects to be 
photographed are highly illuminated. M. Bazin is able to 
remain about ten minutes in his submarine chamber, and 
has produced several clear and well-defined photographic 
pictures of objects at the great depth of three hundred feet. 
Books CuT OR UNCUT.—A correspondent of the A the- 
neum writes, “Ihave no less than seven paper-knives in 
use in my house; but, in common, I dare say, with many 
of your readers, it very often happens that I am unable to 
lay my hands upon one when wanted. I know that to many 
it is a luxury to have the first read of a book, and with 
paper-knife in hand cut away as they read; but I think the 
balance of convenience is on the other side, and I wish to 
take the opinion of the literary world as to whether a period 
of civilization has not arrived when the readers of books 
and periodicals might reasonably ask that they should be 
delivered from the publishers ready cut.” 
A NEW SUBSTITUTE FOR COLLODION.—-M. Persoz, fils, 
has recently discovered a method for obtaining a material » 
possessing the same characteristic qualities as collodion. 
La Lumucre says :—This new substance is produced by dis- 
solving silk in a suitable solvent, and then separating the 
latter by means of dialysis. Ifthe film be of a certain de- 
gree of thickness, it assumes on drying a golden tint, but 
this would no doubt be scarcely perceptible in a thin film, 
such as would be used in photography. The solvent chosen 
by M. Persoz is chloride of zinc, which, when kept at a 
warm temperature, readily dissolves the silk, but if the sol- 
vent be not warmed, the silk takes a much longer time to 
dissolve. Before employing the chloride of zinc, it 1s 
