56 
THE YOUNG SCIENTIST. 
skin from chin to tail, and two transverse 
cuts across the first to a short distance 
along the inner side of the legs, as far 
down towards the feet as the length of 
skin to be removed from the limb requires. 
In case the head is not to be retained, a 
cut is made from the bridge of the nose, 
past the angles of the jaws, to the first cut 
below the chin on each side, so that when 
the whole skin is removed, the included 
portion remains attached to the jaws, 
while the eyelids and ears are removed 
with the rest of the skin, the bone is 
drawn from the tail. The next step is to 
tack the skin, with the hair downwards, 
to a bqard ; stretching it only just suf- 
ficiently to render it quite flat, and put- 
ting the tacks as near the edge as possi- j 
ble. Any adherent fat is then removed | 
with a blunt knife, and the whole surface ' 
slightly scraped. It is then thoroughly 
rubbed with equal parts of alum and salt, 
and set aside for two days to dry. A 
second curing, and in two more days a 
third, are required, and the skin should 
be by the end of a week nearly dry ; but it 
wall be perfectly stiff and hard. 
Taking the blunt knife, the best form of 
which is the ordinary round-pointed table 
knife, the skin is thoroughly scraped, and 
the scraping continued till the hard sur- 
face is removed, and the skin is as pliant 
as washleather. In a day or two more a 
second, very rarely a third, scraping may 
be necessary, and the skin is then fit for 
use, and perfectly sweet. 
There is one beautiful skin which de- 
serves special mention in connection with 
this method of curing — the mole's. The 
best way to preserve it is by making a cir- 
cular incision round the chest, as close to 
the "hands" as possible, and then turn- 
ing the skin inside out over the body ; so 
that as much as possible of the skin is left 
untouched. The method of drying is to 
fit the pocket thus obtained over a wooden 
cylinder, about twelve inches in length, 
and of the requisite diameter, and pro- 
ceeding in the usual way. The hind feet 
maybe cut off close to the skin, as they 
leave no appreciable hole. 
So far I have given an outline which 
may be useful to some of the readers of 
this journal. I do not lay claim to much 
originality in method, but I have tried to 
put myself in the place of a beginner, ii; 
descrilnng the ins and outs of the simple 
process which puzzled myself at first, and 
to give some idea of the way in which I 
have learnt to overcome the difficulties 
I have met with. If I have succeeded, it 
may be that a rare specimen may be saved 
from loss, and I am content. Who knows 
whether, if some Dutchman had only 
known how to make up a skin, there 
might not be a stuffed specimen yet ex- 
isting of the 1)0(10 1— Charles D. Whistler 
in Science Gossip. 
Home-Made Telescopes and Micro- 
scopes.— V. 
ON THE PKODUCTION OF FLAT SURFACES 
IN GLA^SJ. 
THE most important tools required for 
the work are three circular cast-iron 
laps, about 6 inches in diameter, having a 
screwed boss at the back, similar to the 
face-chuck of a lathe. These must be first 
turned flat on their faces, and then scraped 
to a true surface, either from a standard 
planometer, as practiced by engineers, or 
else the three may be scraped together till 
no error can be detected by their inter- 
change. It would, perhaps, be out of 
place to give the details of this operation, 
which is described in most elementary 
works on mechanism. These planes, as 
left by the scraper, are not sufficiently 
smooth for the purpose required; they 
must, therefore, be ground together. One 
of the plates is screwed down on a stud 
fixed in the bench or vice, and a wooden 
knob is fixed into the other to serve as a 
handle; they are then rubbed together 
with fine emery and water, frequently 
interchanging the plates. It is a very dif- 
ficult matter to bring these plates to an 
exact plane by grinding alone, and to keep 
them so during their continued employ- 
ment. The test of their truth is, that after 
they are all wiped clean and dry, and 
rubbed together, the three should present 
a mottled appearance, uniformly covering 
the whole of their surfaces. One cause of 
error is a natural tendency of the grind- 
ing-powder to collect unequally between 
them. This may be somewhat corrected 
