THE YOUNG 
diameters, knowing the diameter of a leaden 
shot, we can compute that of an iron one of 
the same weight. 
Let us call the diameter of the leaden one 
10: then the cube of 10 X 11-25 -f- 7.78 = 
1446; the cube root of 1446 is not quite 11.4, 
the diameter of an iron shot that would have 
the same weight as a leaden one whose diame- 
ter is 10. Now as circles are to each other as 
the squares of their diameters, the resistance 
of the air on an iron shot would be not quite 
130, to 100 for the leaden one. 
Now call the distance which a leaden shot 
will travel 10, then 10 X 100 = 1000, the total 
resistance necessary to stop either shot; 1000 
130 = 8 nearly, so we see that an iron shot 
■of the same weight would lack only one-fifth, 
instead of nearly half the range of a leaden 
•one. This would be correct if nothing but 
the resistance of the air would tend to stop the 
shot; but as gravity would tend equally to 
bring both down, this would act to make both 
somewhat nearer equal. Now if, as is hoped, 
the iron shot would, by reason of not being 
flattened by crowding in the gun, scatter less, 
the effective range might be greater than with 
the leaden ones. Then there is the advantage 
•of their not being poisonous to be taken into 
account. Birds have been killed by picking 
up shot, and a number of people were recently 
very seriously poisoned by lead absorbed by 
vegetables; cows are also said to have died 
from the same cause. H. A. Spkague. 
Charlotte, Me. 
Are Snakes Beneficial? 
Ed. Young Scientist— I was much pleased to 
see that you have a good word for the toad, but 
as your article would seem to indicate that 
toads destroy mice as well as insects— which, 
if true, is new to me— I would ask if you 
meant to be so understood? You also say that 
we should cultivate the friendship of insect- 
ivorous reptiles — including the snake. 
Now I would like to inquire if there is an 
insectivorous snake that does not also eat the 
toad? I and many others have seen snakes in 
the aet of swallowing the toad. It is evident 
that snakes of this class ought to be destroyed, 
but there may be a purely insectivorous snake. 
If there is will you please describe it, so we 
shall know it from the harmful kinds. 
H. A. Sprague. 
SCIENTIST. 59 
BOOK NOTICES. 
TKe Boy E^ngineers : What They Did and How 
They Did it. A Book for Boys. By the Rev. J. 
Luken, author of "The Young Mechanic," 
"Amongst Machines," etc. New York: G. P. 
Putnam's Song. 
The term " engineer," as used in this book, will, 
we are afraid, convey somewhat erroneous ideas to 
our American boys. The construction of engines 
and machines is certainly "engineering" in the 
strict sense of the word, but we are not accustomed 
to associate this term with the construction of 
wooden clocks and organs, or with the art of carv- 
ing. Be this as it may, however, the book is a 
capital one. It details in simple language the work 
of two boys in making lathes, clocks, automata* 
engines, organs, apparatus, etc. It tells of their 
difficulties, and the means by which they sur- 
mounted them, and gives a great many very valu- 
able hints and suggestions. Our readers, old or 
young, who may procure this book, have a rich 
treat in store for them. 
United States Official Postal Guide : April, 
1878. Price 50 cents. Boston: Houghton, Os- 
good & Co. 
This valuable publication is published in pursu- 
ance of an express law to that effect, and with the 
authority and co-operation of the Post-Office De- 
partment at Washington. It contains an alpha- 
betical list of post offices in the United States, with 
county. State and salary; money order offices, do- 
mestic and international; chief regulations of the 
Post-Office Department; instructions to the public; 
foreign and domestic postage tables; schedules of 
the arrival and closing of mails at the principal 
cities, arrival and departure of foreign mail steam- 
ers, with other information. It is absolutely indis- 
pensable to every man whose business involves the 
use of the mails. 
A Lady Editor. _A mechanical journal is pro- 
bably the last amongst the numerous periodicals 
now published that we would expect to find edited 
by a lady, and yet " The Mechanic," published at 
Smithville, N. J., is one of the most judiciously 
conducted journals of its class, and does great 
credit to the editor, Mrs. Smith. The terms are 
$1.00 per year. 
A Call to the Telephone. — Several devices 
have been suggested for calling attention to the 
telephone, when it is desired to open conversation. 
Most of them are clumsy, and some require the at- 
tachment of a galvanic battery. One of the simplest 
is described and figured in " Nature." It is the in- 
vention of W. C. Rontgen, and consists principally 
of a tuning fork (Ut 4), one of whose prongs is 
brought close to one of the poles of the magnet in 
the telephone — preferably to the pole farthest from 
