70 
THE YOUNG SCIENTIST. 
their younger brothers. For example, the 
article on kites has been inquired about by 
some of our lady subscribers, because they 
wished to find out the best way of making 
a kite to amuse some little boy. But we do 
not intend that the unselfish nature of the 
girls shall be taxed too severely, and we 
promise them important aid in their own 
special departments. Of course there is a 
wide range of subjects common to both 
boys and girls. Thus, the microscope, about 
which we shall always have at least a couple 
of pages, is used quite as frequently by 
girls as by boys, and often more efficiently 
by the former than by the latter. So, too, 
all subjects which merely give information, 
such as most articles on natural history. 
The care of pets, too, is often as great a 
source of pleasure to girls as to boys. But 
in addition to all this, we have made pro- 
vision for special articles on subjects pecu- 
liarly interesting to girls, and such as they 
are not likely to find discussed in journals 
published exclusively for ladies. 
A Cheap Condensing Lens. 
SUCCESS in the use of the microscope 
depends very largely upon proper 
management of the illumination. Some 
objects require a soft and subdued light; 
others demand the most intense illumina- 
tion that can be obtained, and the various 
ways in which the light ought to be modi- 
fied so as to produce the best results, are 
more numerous than most persons are 
aware of. Amongst the numerous accessories 
used for purposes of illumination, none are 
more useful, or give better results, than the 
condensing lens or bulls-eye condenser. And 
here let us explain the difference between 
these two: The bulls-eye condenser ought 
to be a hemispherical lens; a condensing 
lens may have any degree of curvature. 
Until within a few months the condensing 
lens has been a somewhat expensive acces- 
sory, none being for sale at a less price than 
four to ten dollars. We have so often ob- 
tained really good results, however, by 
means of very cheap and simple arrange- 
ments that we shall describe a simple affair 
which we once made, and which seemed to 
work about as well as far more expensive 
articles. Any intelligent boy or girl can 
make one. 
The thing that is required first is a suita- 
ble lens. We found that one of the best 
lenses for this purpose is what is called by 
spectacle makers a cataract lens, of as high 
a power as can be had; No. 2 answers very 
well. Such lenses have a short focus — 
about 2 inches — and are about an inch and 
a half in diameter. The cost varies from 
15 to 25 cents, according to the profits de- 
manded by the dealer. 
Fig. 1. 
Where a cataract lens cannot be had, very 
good work may be done with some of the 
cheap lenses sold for burning glasses. In 
general, however, they have too long a 
focus. A good substitute for a lens is a 
small glass bulb filled with water. This we 
shall describe at some future time. 
Having procured a lens, the next thing is 
to mount it. This is easily done. Get a 
common letter file, such as can be had for 
Fig. 2. 
10 cents, or make one by inserting an up- 
right wire in a block of wood, as shown in 
Fig. 3. Procure also a good bottle cork; a 
piece of wire about 6 inches long, and one- 
eighth of an inch in diameter; and a strip 
of tin about three-eighths of an inch wide 
and six inches long. Bend the tin into a 
loop, as shown in Fig. 1, the loop being the 
