events free from grease--in order to obtain the best results.

M. Margot has contributed further information to the Archives des
Sciences physiques et naturelles (February 1895). He finds that
adherence between aluminium and glass is promoted by dusting the glass
with powders, such as rouge. There is no doubt that a considerable
improvement is effected in this way; both rouge and alumina have in
my hands greatly increased the facility with which the aluminium is
deposited. M. Margot finds that zinc and magnesium resemble aluminium
in having properties of adherence to glass, and, what is more, carry
this property into their alloys with tin. Thus an alloy of zinc and
tin in the proportions of about 92 per cent tin and 8 per cent zinc
may be melted on absolutely clean glass, and will adhere strongly to
it if well rubbed by an asbestos crayon.

A happy inspiration was to try whether these alloys would, under
similar circumstances, adhere to aluminium itself, and a trial showed
that this was indeed the case, provided that both the aluminium and
alloy are scrupulously clean and free from oxide. In this way M.
Margot has solved the problem of soldering aluminium. I have satisfied
myself by trial of the perfect ease and absolute success of this
method. The alloy of zinc and tin in the proportions above mentioned
is formed at the lowest possible temperature by melting the
constituents together. It is then poured so as to form thin sticks.

The aluminium is carefully cleaned by rubbing with a cuttle bone, or
fine sand, and strong warm potash. It is then washed in water and
dried with a clean cloth. The aluminium is now held over a clean
flame and heated till it will melt the solder which is rubbed against
it. The solder sticks at once, especially if rubbed with another bit
of aluminium (an aluminium soldering bit) similarly coated. To solder
two bits of aluminium together it is only necessary to tin the bits by
this process and then sweat them together.

The same process applies perfectly to aluminium caused to adhere to
glass by the previously mentioned process, and enables strong soldered
contacts to be made to glass. In one case, while I was testing the
method, the adhesion was so strong that the solder on contracting
while cooling actually chipped the surface clean off the glass. In
order to get over this I have endeavoured to soften the solder by
mixing in a little of the fusible metal mercury amalgam; and