12 
THE YOUNG SCIENTIST. 
make the nest of something that may be dipped 
occasionally in boiling water. Half the diseases of 
cage birds are caused by these almost invisible 
parasites. Mounted in glycerine jelly, they form 
very interesting microscopic objects. 
A Good Mucilage. —It is said that a mixture of 
one part of dry chloride of calcium, or two parts of 
the same salt in the crystallized form, and thirty- 
six parts of gum arabic, dissolved in water to a 
proper consistency, forms a mucilage which holds 
well, does not crack by drying, and yet does not 
attract sufficient moisture from the air to become 
wet in damp weather. 
Brass Lacquering—If you want a good deep 
gold lacquer, you should make up a small stock 
bottle, holding, say, half a pint, according to the 
follawing recipe; you can then add as much as, 
may be required for the tint you wish to get: Alco- 
hol, I pint; dragon's blood, 1 dram; seed lac, 
oz.; turmeric, ^oz. Shake up well for a week, at 
intervals of, say, a couple of hours; then allow to 
settle, and decant the clear lacquer; and if at all 
dirty, filter through a tuft of cotton wool. Mix 
with the pale lacquer a day or two before you wish 
to use it. 
Ink tliat will not Freeze. — Mr. H. A. 
Sprague, having tried a mixture of alcohol with ink, 
found that the compound spread and was useless. 
He then tried glycerine mixed with ink, and found 
it too thick. Finally he tried a mixture of equal 
parts of concentrated glycerine, alcohol and water, 
deeply colored with aniline black. This mixture did 
not freeze in the coldest weather, it flowed freely 
from the pen, and did not spread. Our only fear 
would be that such ink would not dry thoroughly. 
Magnifying Power—Few persons have a clear 
notion of the magnifying powers that have been or 
can be obtained by means of the microscope. The 
following will be found trustworthy: A common 
hand magnifier, 1 inch focus, magnifies ten times; 
very strong glasses, twenty times; small globule 
lenses, such as were sold for 25 cents, about 50 to 
75 times; the most powerful single lenses that can 
be generally used, 150 times; the most powerful 
single lenses ever found available, 300 times; ordi- 
nary compound microscopes, highest power from 
250 to 500 times; highest power ordinarily obtained 
with the best microscopes, 1,500 times; highest 
power yet obtained, giving fair light and definition, 
15,000 to 20,000 times. Claims have been made for 
much higher powers, but such claims are generally 
ignored by the best microscopists. By times we 
mean, in all cases, diameters. Sidewalk opticians 
generally mean areas when they speak of times. 
Areas are found by multiplying the diameters by 
themselves. Ten times, mentioned above, is 100 
areas. The cheap microscopes said to magnify 
1,000 times, magnify about 33 diameters. 
BOOK NOTICES. 
A Treatise on Engineering Construction: 
Embracing Discussions of the Principles Involved, 
and Descriptions of the Material Employed in 
Tunnelling, Bridging, Canal and Koad Building, 
etc., etc. By J. E. Shields, C. E. 44 illustra- 
tions. New York: D. Van Nostrand. 
It would, very evidently, be utterly impracticable 
to present, in 138 pages, anything hke a full state- 
ment of the principles involved in the branches of 
engineering discussed in this book. Between the 
elements of the subject, however, which are known 
to every young engineer, and those higher depart- 
ments of study which are practically valuable only 
to those professional engineers who make a specialty 
of certain departments of construction, there lies 
an important range of applied science, which is 
of the utmost value to others besides professional 
engineers. This is the field which Mr. Shields has 
attempted to occupy, and he has done his work 
well, giving in clear and concise form just that 
practical information required in the every day 
work of the engineer, the builder, the architect, 
etc. Viewed from this standpoint, the work must be 
regarded as one of great value to a very large class. 
The Gas Consumer's Handy Book. By Wil- 
liam Richards, C. E. London and New York: E. 
& F. N. Spon. 
A great deal of the trouble which arises between 
gas companies and their customers is caused by the 
ignorance of the latter, and this little book will 
serve a useful purpose in helping to remove these 
difificulfcies, if it should do nothing else. But it will 
do more than this. It will enable every gas con- 
sumer to get the greatest possible amount of good 
from the gas which he consumes. It will effect this 
in two ways: first by teaching how to use the arti- 
cle effectively, and, secondly, how to avoid the evil 
effects which it is apt to produce when burned 
without proper attention to ventilation and the 
effect of strong light on the eyes. The work is 
simple and reliable, and should be in the hands of 
every householder that uses gas. 
. ♦ . 
EXCHANGES. 
In this column yearly subscribers who may wish 
to exchange tools, apparatus, books, or the pro- 
ducts of their skill, can state what they have to 
offer and what they want, without charge. Buying 
and selling must, of course, be carried on in the 
advertising columns. 
Wanted, a small turning lathe, about 1^ inch 
swing, and 12-inch bed; must be well made; books 
and apparatus in exchange. R. M., care of this 
journal. 
Wanted, a copy of Holtzapfel's "Mechanical 
Manipulation." State what is wanted in exchange. 
E. W., Box 4875, New York. 
Wanted, a good aquarium, medium size. State 
what is wanted in exchange. E. H., 8 Beekman 
Place, New York. 
