78 
THE YOUNG SCIENTIST 
The Pneumatic Paradox. 
This singular experiment was first brought to 
the attention of the public about fifty years ago, 
and although known to readers of technical 
THE PNEUMATIC PAKADOX. 
journals., seems to have escaped the notice of 
the writers of our ordinary works on natural 
philosophy. 
The only materials required are two discs of 
card or wood, and a tube which may be of glass, 
metal, or even tobacco-pipe stem. 
From a stift" card cut two discs or circles 
about two and a half inches in diameter. One 
is to be left plain, and through the centre of the 
other punch a hole the same size as the outside 
of the tube. Then fasten to the under side of 
the card, with sealing-wax or paste, a piece of 
cork with a hole in it the same size as that in 
the card. This is to make a bearing for the 
insertion of the tube. 
To make the tube, the best material is a piece 
of glass tubing about a quarter of an inch in 
diameter. This may be bent in the flame of a 
common spirit-lamp, and inserted in the cork, 
as shown in the engraving, when the apparatus 
will be complete. Where glass is not procur- 
able, any tinsmith can make a tin tube that will 
answer the same purpose. If carefully bent 
over the thumb, it may be curved without flat- 
tening or wrinkles ; but those who do not suc- 
ceed in this way may first fill it with sand or 
melted rosin, and it may then be bent without 
danger. 
Having constructed this very simple little ap- 
paratus, it will be found that the utmost power j 
of the lungs will fail to blow the upper disc off 
the lower one. Nay, more : If the position of 
the instrument, as shown in the figure, be re- 
versed, so that the disc attached to the tube 
shall be uppermost, and the loose one below it, 
it will be found that on blowing through the 
tube the loose disc will not fall away from the 
other one, but will adhere strongly to it ! The 
loose disc may even be attracted from a short 
distance, say half an inch, and actually raised 
up by the stream of air which presses against it 
from above ! 
This little apparatus, which any boy or girl 
can easily make, may give rise to a good deal of 
amusement. Most persons, if asked if, by tlie 
force of their lungs, they can raise a cent laid 
on the upper card, will answer Yes " 
I On trying it, they are sure to fail, 
and at first think that it is the cent 
that keeps the card down. They will 
be greatly surprised to find that they 
cannot lift the bare card, and still 
more astonished when they see that 
it is totally impossible to blow the 
loose card away, even when the in- 
strument is turned upside down, as- 
we have just described. 
The principles involved in the action 
of this little instrument are not very 
easily explained, and although many plausible 
solutions have been given, a good deal of uncer 
tainty still hangs over the subject. 
BOOK NOTICES. 
Ornamental Penman's, Engraver's, 
bign-Writer's and Stone-Cutter's Pocket Booi 
ot Alphabets. London and New York- E & P 
This is a neat little oblong i2mo volume, con- 
taining thirty-two plates of alphabets, it will 
prove specially valuable to those who wish to 
finish off their drawings handsomely by a neat 
title, for it is a fact well known to every draughts- 
man that while a poor drawing, well lettered, may 
present a tolerably respectable appearance, the 
very best drawings may be spoilt and rendered 
repulsive by poor lettering. One great point in 
favor of this little book is its moderate cost. 
Practical Instruction in Animal Magnet- 
ism. By J. P. F. Deleuze. Translated by Thos. 
Hartshorn, Revised edition, with an Appendix^ 
of Notes by the Translator, with Letters from 
Eminent Physicians and others descriptive of 
Cases in the United States. i2mo, pp. 524 cloth 
Price $2. New York: Samuel R. Wells & Co. 
This subject is one to which we have given very 
little attention, and consequently we do not feel 
able to pronounce an opinion in regard to the 
value of this work. It is a large volume, neatly, 
got up, and for those who desire to study the sub- 
ject, we should consider it a most desirable work. 
Section Cutting. A Practical Guide to the 
Preparation and Mounting of Sections for the 
Microscope ; Special Prominence being given to 
the Subject of Animal Sections. By Sylvester 
Marsh. Reprinted from the London edition. 
With Illustrations. l2mo., cloth, gilt title. Price 
75 cents. New York: Industrial Publication 
Company. 
The majority of the most important objects 
studied by the microscopist, demand for their 
thorough examination that they be reduced to 
thin sections. The ordinary works on the micro- 
scope are somewhat meagre on this special 
branch of laboratory work, and Dr. Marsh has 
