146 THE YOtNl 
The bellows is worked by the foot, and 
the air passing through the rubber tube 
s, and the glass pipe a, is compressed in 
the bottle by reason of the smaller di- 
ameter of the exit pipe c, causing a con- 
tinuous and uniform current of air, which 
can be still further controlled by open- 
ing or closing the cock v. If it is de- 
,sired to introduce warm air into the cater- 
pillar-skin, the bottle k may be placed 
upon a sand bath. The size and fineness 
of the i)oint of the glass pipe e upon 
which the skin is secured, depends upon 
the size of the caterpillar, therefore sev- 
ral sizes of them should be at hand. 
To fasten the skin upon the glass-point, 
wind a common insect-pin around the 
glass, bend it along the pipe and make a 
small hook of the pin point, (See Fig. 2) 
or bind with thread two springs to the 
pipe, as shown in Fig. 3, having them 
bent rectangularly at the end, and the 
tips fitted to the pipe. Fig. 4. 
Collodio Etching— II. 
BY BENJAMIN HARTLEY. 
BEFOKE taking up the several details 
of the picture, I must go back a step 
to say a few words more about the plate. 
In the last number, I said that the plate 
had better be varnished when beginning 
to practice. Supposing, now, that you 
had made the attempt, you have dis- 
covered that the varnish is rather hard to 
scratch, and that is just why I told you 
to use it. When you draw on the collo- 
dion film without it's being varnished, you 
have to be exceedingly careful, as the film 
is very tender and delicate. Now I im- 
agine you sitting with your unvarnished 
plate, and I know your first question must 
be, " How shall I get my sketch trans- 
ferred to it? ' ' Of course you cannot do 
as before intimated, that is, turn it over 
and rub it on the back, for by so doing 
you would ruin your plate. You must 
draw it directly on the film. This is 
somewhat difficult with a pencil, because, 
no matter how soft it is, it will now and 
then catch on some particle of grit, and 
make a line through the film when you 
only desire a tracing on the top, to be 
filled up afterwards by very different 
SCIENTIST. 
lines with the needle. You require first 
simply to " block in " your subject, and 
for doing this you will find a very small, 
sharp-pointed stump or blender to be the 
most useful tool. Those made of wash 
leather are to be preferred to the paper 
ones, provided they have good points. 
With one of these stumps you can indi- 
cate the outline, and, if used gently, the 
false strokes will not injure the drawing. 
When your picture is thus sketched, you 
take your finest needle and proceed with 
the distance as before stated. 
The reversing of the picture is another 
point I promised to explain. If the pic- 
ture to be copied is not just the right size 
for your plate, you must make an outline 
sketch of it, the proper dimensions. 
Then, placing a piece of transfer paper 
on your table or drawing board, put on it 
a piece of drawing paper, and on the top 
lay your sketch and go over the lines with 
a pencil or ivory point. When this is 
done you will find on lifting the paper an 
exact reversal of your subject which you 
can easily copy on the plate. 
Now we will take up the details of the 
picture. I can only give a few general | 
hints, but hope they will be sufficient to | 
guide the amateur in his studies. First i 
then, take the water. If it is still, as in a i 
pond, or smoothly fiowing, as in a deep 
river, the lines must be kept very straight, ! 
both horizontally and perpendicularly, j 
in order to give the effect of transparency \ 
and flatness. Let the lines be few, ex- \ 
cept in the reflections. To represent the j 
current of a stream, lines are used which \ 
are sometimes curved, but more frequently | 
straight, although not horizontal, as j 
they all run towards some perspective dis- j 
stance or vanishing point. In broken , 
water, such as rapids, cascades, etc., the ; 
lines must follow the direction of the 
flow. To study the finer points of treat- 
ment you must examine closely the best 
etchings and engravings you can find. 
In regard to trees, I would remark that ! 
if they are in the distance, the small i 
curved lines are the best— a series of 1 
little curves forming the outline of the 
tree or bush. If they are near the fore- 
ground, then you must show the character 
of the tree in the treatment of the trunk, \ 
