THE YOUNG 
ends of their feet enclose an amount of 
air which enables them to float. As each 
foot is put down it forms a sort of cup- 
like depression in the water, and the 
INSECT WALKING ON WATEK. 
liquid thus displaced is sufficient to float 
the insect. 
Our young readers will have no diffi- 
culty in making the iron wire or needle 
float on a basin of water, and the experi- 
ment is a most astonishing one to those 
who see it for the first time. 
Webb's Celestial Objects for Common 
Telescopes. 
OUE readers will be glad to learn that 
the new edition of this work, which 
has been so long out of print, is nearly 
ready for delivery. The author has re- 
vised it with great care, and has added 
very considerably to the amount of matter 
which it formerly contained. 
Any comments at our hands on this well- 
known book are unnecessary^ It is just 
the manual for every amateur astronomer, 
whether he owns a telescope or not. To 
those who possess a telescope, or who in- 
tend to purchase one, the book is simply 
indispensable. So fully are we impressed 
with the value of this book, that we have 
arranged for a special edition, and are 
thus enabled to offer it at a considerably 
lower price than it would otherwise com- 
mand. 
We have the advance sheets now before 
us, and expert the complete work in a few 
days. The price will be $3, for which sum 
the book will be sent to any address in 
the United States or Canada. 
New Copying Process. 
Mr. Adler has communicated to the Photo- 
graphic Society of Vienna a new copying pro- 
cess, based upon the use of the glue glycerin 
pad, which is employed in the hectograph. For 
the purpose of the new process, however, the 
pad must contain more glue. The writing or 
drawing is made upon paper with a concentrated 
solution of alum, to which a few drops of aniline 
SCIENTIST. 37 
ink are added, to make the letters or figures 
visible on the paper. Before transferring this 
to the pad, the latter is wiped with a damp 
sponge, and the moisture is allowed to remain 
a few minutes to make the surface sufficiently 
absorbent. The paper is now placed on the pad, 
written side down, and, after a few minutes, 
again removed, when the writing or drawing 
will be transferred to the pad. By means of a 
rubber roller a small amount of printer's ink is 
now applied to the surface ; the ink will adhere 
only to the lines made by the alum solution. A 
slightly damp sheet of paper is now placed upon 
it, and, by gentle rubbing, the Avriting trans- 
ferred to the latter. It is necessary to ink the 
pad each time, but a large number of impres- 
sions may be taken, and the prints have the ad- 
vantage of being permanent and hlsick.—Pharm. 
Centralh., No. 49. 
Preparation of Bone for Turning. 
Leg or marrow bones are best : get them and 
saw off both knuckle ends or joints; with a. 
hooked wire draw the marrow out, put them on 
the fire in a boiler or saucepan, with some water, 
and subject them to a simmering heat, which is 
far better than galloping them out of the pot. 
After two hours stewing, put by in the liquor 
until cold, then take them out, dry well in saw- 
dust, and transfer to some powdered quicklime. 
In a few days they will be fit for use, and may 
be cut up into rings or strips.' Keep them in 
the lime until wanted ; thus you will have bone 
equal in appearance to best ivory. 
Horse bones are best; ox, sheep, and other 
animals do for smaller work, but generally I go 
to the shops that dress cow-heel or neats-feet, 
and tripe, and get the finest bones for general 
purposes. — English Mechanic. 

Tlie Relative Cost of Motive Power. 
M. Bissinger, M. E., at Carlsruhe, Germany, 
gives the following results as obtained in his 
examinations of the several motors in regard to 
the relative cost per horse for each hour. It 
will be observed that the examination pertained 
principally to small motors. The relative cost 
per effective horse-power per hour is as follows : 
loo-horse power steam engine 7-6 
2-horse power steam engine 44-3 
2-horse power I^ehmann's caloric engine 26.5 
2-horse power Hock's motor 40.0 
2-horse power Otto gas engine 26.4 
2-horse power Otto Lang gas engine 26.4 
2-horse power Schmidt's hydraulic motor, sup- 
plied with water from the city water works 95- 00 
2-horse power obtained by horses and a gin 45-oo 
2-horse power obtained by manual labor 200.00 
Otto's gas motor and Lehmann's caloric engine 
are the cheapest of the small motors, but are, 
nevertheless, four times as expensive as the 100- 
horse power steam engine. 
