THE YOUNG SCIENTIST. 
57 
Always, after using soldering fluid, wash off 
the joint carefully with pure water. 
A very little experience will enable any one 
to join almost any two pieces of metal, and to 
solder a patch upon a metallic vessel. 
Entomologist's Pliers. 
Some time ago a friend showed us a very 
handsome pair of forceps, which had been made 
for the purpose of taking insects out of their 
cabinets and replacing them. In most cases 
insects are preserved by being impaled on 
slender pins, with heads like ordinary pins, 
and in order to examine any particular insect, 
it is necessary to pull the pin out of the cork 
lining of the cabinet. In doing this with the 
fingers alone, one is very apt to injure the 
insects on the adjoining pins, and therefore 
our friend had procured the forceps just men- 
tioned. Such forceps, however, were open to 
two objections; they did not grasp firmly the 
ENTOMOLOGICAL PLIBRS. 
round head of the pin, and the legs being levers 
of the wrong kind, the power applied was 
greatly wasted. 
By taking a pair of common steel pliers, and 
softening the nose in the fire, a hollow may be 
filed in each blade, as shown in the engraving. 
This hollow receives the head of the pin, 
while the part just below the head is grasped 
with great firmness by a very slight exertion of 
power. By means of pliers fixed in this way, 
insects mounted on pins may be very readily 
taken out of their cabinets and replaced. The 
pliers may be rehardened if desired, and are 
then as good as ever for the purposes for which 
they were originally intended. 
Tempering Small Steel Tools. 
The art of tempering small tools is by no 
means difficult to acquire, and when we have 
learned to do it well, we can often save a great 
deal of time and trouble, by doing it ourselves, 
instead of having to go to a distance. 
There are two distinct operations in the pro- 
cess of tempering. We must first harden the 
tool, and then let it down, as it is called, or 
soften it so that it will no longer be brittle, the 
rule being that a tool should be as soft as pos- 
sible, provided it will keep its edge. Thus 
tools intended for cutting wood are always 
much softer than those used for cutting metal. 
To tempera tool proceed as follows: Heat it 
to a bright red, and plunge the part to be 
hardened into water. We hear a great deal 
about secrets in the art of hardening, but they 
amount to very little. Some add salt, arsenic 
and other things to the water in which they 
harden steel, and claim to get much better re- 
sults by so doing. The truth is that well 
boiled water is as good as any ordinary mate- 
rial. Fresh water has so much air in it that it 
will not harden steel well, because the air 
forms a ttin coating on the steel, and prevents 
contact with the water, and the steel is a long 
time in cooling. Hence we find that black- 
smiths like old water, that has been used a long 
time, for hardening. The reason is that the 
air has been all expelled, and if a little oil has 
been dropped in the tank, it will have kept the 
air out by covering the entire surface with a 
thin film. Small tools are sometimee hardened 
in mercury, and can be made very hard in this 
way. Small drills are often hardened by being 
heated in the flame of a candle, and then cooled 
by being thrust into the tallow. This answers 
well, but is no better than water. The mechan- 
ical journals often contain what is said to be a 
very valuable recipe for tempering, which is to 
plunge the heated tool into sealing-wax. This 
answers well, but has no special advantages. 
Very small tools and thin plates may be har- 
dened by waving them rapidly in the air, and 
