THE YOUNG SCIENTIST. 
143 
thoroughly saturated with the latter it 
should be mounted in Canada balsam. 
From caterpillars it is easy to procure 
not only the spiracles but the connected 
air tubes or trachea3. These form very 
beautiful objects when perfectfy dissected 
and well displayed. The best method of 
preparation is to slit the caterpillar open 
along the under side and soak it in acetic 
acid. After a day or two the entire system 
of tracheal tubes may be separated by 
means of fine needles, and after washing 
with water, and soaking in alcohol and 
turpentine, they may be mounted in bal- 
sam—or after washing with alcohol they 
may be mounted in glycerine. 
Notes on my Cabinet. 
THE microscope is not only a means of 
education and a tool for accomplish- 
ing valuable practical work, but, also a 
source of great pleasure and amusement 
from the endless variety of beautiful and 
curious things which it enables us to ex- 
amine. And, although many; scientific 
men look down upon such a use of the in- 
strument, to my mind it is one of great 
value and usefulness. An evening spent 
over the microscope, even by those who 
have but little scientific knowledge, tends 
to elevate and improve. 
Nothing tends so much to enhance the 
pleasures of such an evening as a good 
supply of interesting slides or objects. 
They need not be very costly .or even of 
much scientific value; if they show the 
objects well and bring out clearly a few 
important points, it is all that is required. 
But, in order to get the greatest enjoy- 
ment out of such an evening, it is neces- 
sary that we should have something which 
will exercise our minds as well as our eyes. 
I make no pretensions to being a micro- 
scopist, and the instrument which I use 
would probably be ridiculed if introduced 
at any of our modern microsco} ical exhib- 
itions. But, by means of it I have been 
enabled to give a great deal of pleasure to 
friends, young and old, and, perhaps, a 
few leaves from my experience may not 
be unacceptable to readers of the Young 
Scientist. 
Some objects can only be kept on hand 
w^hen carefully mounted on glass slips. 
This is the case with different kinds of 
blood and with all objects which are diffi- 
cult to procure, and which require much 
time for preparation. But I have always 
found that the objects which give the most 
pleasure to a gathering of a few friends 
are not the finely mounted slides but those 
common objects which are easily found, 
easily prepared, easily mounted, and easily 
shown. A few evenings ago some friends 
called at my house, and out came the in- 
evitable microscope. I first showed them 
some slides of diatoms and other scientific 
things which i:>loased them much, and 
greatly excited their wonder when they 
came to see that the large and elaborately 
carved shells which were so beautiful un- 
der the microscope were entirely invisible 
to the unassisted eye. But, after all, there 
was a kind of feeling as if the microscope 
had made these things, not as if it merely 
enabled us to see things that were already 
in existence and which merely required 
keener vision to render them sensible. 
After a while, however, a lull took place 
in the exhibition, and the conversation 
wandered off to other matters. One lady 
incidentally mentioned that she had pur- 
chased, very cheaply, some material which 
was warranted all wool, but which she 
feared was partly cotton. As she had the 
stuff with her I suggested that it would be 
very easy to settle the question by an ap- 
l->eal to the microscope. So a little of the 
fabric was cut off, placed on a slide, and 
teased out with common needles stuck in 
pine handles. It was then moistened with 
a little glycerine and water and covered 
w^itli a thin glass. On placing it under the 
microscope it was at once seen that the 
material was, at least, three-fourths cot- 
ton, and this was so obvious to every one 
that looked at the object, that the utmost 
surprise and pleasure was shown by all. 
No diatom, however beautiful, could have 
excited the same interest as these few 
fibres of cotton and wool. 
In my next letter I will tell my readers 
something more of these appearances and 
describe to them the best way of examin- 
ing such objects. 
O. 
