188 
THE YOUNG SCIENTIST. 
one can talk into both at the same time, 
and get tlieir combined effect upon the 
line connecting the two. It seems to 
matter little, however, what instru- 
ment is used, for the various experi- 
ments that have been made with different 
points at a great distance have all been 
attended with similar results. It is 
thought, therefore, that the great success 
attained must be attributed to the com- 
pound copper wires of the Postal Tele- 
graph Company, through which the 
sounds are transmitted. They consist of 
a core of steel surrounded by a coating 
of copper, so combining the strength of 
the ordinary wires with the conductivity 
of the copper covering. With these wires 
there appears to be no limit to the pos- 
sible use to which telephones can be put. 
Every word that was said in the Chicago 
office could be heard as distinctly as 
when using the wires that run from office 
to office in this city, and the oi^erators in 
Chicago were able readily to distinguish 
the voices of the gentlemen in the New 
York office. "We see no reason wh^^ some 
of our boy readers cannot construct tele- 
phones in their own houses, or from 
there to the houses of some of their near 
friends. Telephones are easy to make 
and both useful and amusing, as a great 
deal of innocent fan can be taken out of 
them when known friends are at each 
end. In future issues of the Young Sci- 
entist Ave intend giving this subject our 
attention, and hope to give such instruc- 
tions and illustrations as will enable 
many of our readers to construct tele- 
phones of their own. 
We believe it was John B, Gough who 
said that " if you want to succeed in the 
world, you must make your own opportu- 
nities as you go on." Young people who 
are always waiting, Micawberlike, for 
"something to turn up," wait long and 
Avearily. It is folly of the most idiotic 
kind to sit by the wayside and wait for 
some one to invite you to ride in his 
carriage to prosperity and fame. We are 
sure none of our readers— boys or girls — 
are of the dillydally sort, that are afraid 
to take hold of work in all its phases, and 
persistently stick to it until a satisfactory 
end is attained ; but it may bo that some 
of our young friends may not be the 
worse for reminding that thoroughness,, 
expertness and competency are only ob- 
tained by persevering and persistent 
workers, and tljat, without these quali- 
ties, no opportunities for honest advance- 
ment are i^ossible. It is only the com- 
petent and industrious that can make 
opportunities and take advantage of 
them. There is no rest for the pros- 
perous, and there is none required, for to 
be busy is to be happy, and to be happy 
is to be good and useful. 
The Engineer's Slide-Rule and its Applica- 
tions. Beiim' a complete inveytigatioii of tlie 
principles upon wliicli the slide-rule is con- 
sti'ucted, tog:etlier witli the method of its appli- 
cation to all the purposes of the practical 
mechanic. By William Tonkes. Industrini 
Publication Company, New York. Paper. Price 
25 cents. 
This exceUent httle treatise on the engineer's 
slide-rule is an advanced companion of work 
manual No. 2, Tlie Mechanic's Slide-Rule, and 
How to Use it." Both are particularly good works 
for mechanics, the one under notice being espe- 
cially adapted to the wants and requirements of 
students in meclianical and civil engineering. 
Young men who are preparing themselves for 
following any of the constructive pursuits would 
find it very much to their advantage to become 
ocquainted with the workings of the slide-rule. 
The study is not a difficult one, and when once 
mastered, is capable of being applied with ex- 
ceeding rapidity to the solution of some of the 
most tedious and irksome problems. Indeed, 
the slide-rule, in the hands of an expert, is a kind 
of an elastic calculating machine, and is made to 
perform some of tlie most difficult and perplex- 
ing feats in mathematics with a minimum of 
labor. The book under review^ explains how 
these things are accomplished, and tells the rea- 
sons why the solutions may be performed by the 
rule clearly and in the simplest of language. 
The American Boy's Handy Book. What 
to do and How to do it. By D. C. Beard. 
Chas. Scribiier's Sons, New York, 1882. 
This is really what its title claims it to be: 
" The American Boy's Handy Book." The object 
of the work is to teach boys not only how to use 
their toys and playthings, but also how to make 
and care for them, and this, we think, the author 
strives to do in an easy and pleasing manner. 
The chapters on kites are clear and interesting, 
and the instructions given for making these 
aerial playthings are simple and to the point. So 
also are the instructions for amateur boat-build- 
