und that fusible metal either stuck to or contracted
upon clean quartz so as to make a firm joint. In the light of M.
Margot's researches (already described), it occurred to me that
perhaps my experience was only a special case of the phenomena of
adhesion investigated with so much success by M. Margot. I therefore
tried whether the alloy of tin and zinc used for soldering aluminium
would stick to quartz, and instantly found that this was indeed the
case.

Adhesion between the alloy and perfectly clean quartz takes place
almost without rubbing. A rod of quartz thus "tinned" can be soldered
up to anything to which solder will stick, at once. On applying the
method to thick quartz threads, success was instantaneous (the threads
were some preserved for ordinary galvanometer suspensions); but when
the method was applied to very fine threads, great difficulty in
tinning the threads was experienced. The operation is best performed
by having the alloy on the end of an aluminium soldering bit, and
taking care that it is perfectly free from oxide before the thread is
drawn across it. There was no difficulty in soldering a thread
"tinned" in this manner to a copper wire with tinman's solder, and
the joint appeared perfect, the thread breaking finally at about an
inch away from the joint.

I allow Mr. Boys' method to stand as I have written it, simply because
I have not had time as yet to make thorough tests of the durability of
"Margot" joints on the finest threads; but I have practically no
doubt as to its perfect applicability, provided always that the solder
can be got clean enough when melted on the bit. Very fine threads
will require to be stretched before tinning, in order to enable them
to break through the capillary barrier of the surface of the melted
solder.

Sec. 92. Soldering.

It is almost unfair to the arts of the glass-blower or optician to
describe them side by side with the humble trade of soldering.
Nevertheless, no accomplishment of a mechanical kind is so serviceable
to the physicist as handiness with the soldering bit; and, as a rule,
there is no other exercise in which the average student shows such
lamentable incapacity. The following remarks on the subject are
therefore addressed to persons presumably quite ignorant of the way in
which soldering is carried out, and do not profess to be more than of
the most elementary character.

For laboratory purposes three kinds of solder are in ge