t importance is the essential difference between the
melting points of the objects to be brazed or soldered, and that of the
solder used. The latter must always be lower than the former. This
explains why soldering materials are used in a large range of
temperatures. A few will melt at the temperature of boiling water. At
the other extreme 2000 deg. Fah. is required to melt a solder for
brazing. If this point is neglected, it will often happen that the
object to be soldered will fuse before the solder melts. This accident
may occur in the soft Britannia and white metals at the one extreme, and
in the softer brasses at the other. It would not do, for example, to use
flanges of common brass, or even ordinary gun-metal, to be brazed to
copper pipe, for they would begin to fuse before the joint was made.
Such flanges must be made of nearly pure copper, to withstand the
temperature, usually 98 of copper to 2 of tin (brazing metal). A most
valuable feature in solder is that by varying the proportions of the
metals used a great range in hardness and fusibility is obtainable. The
useful solders therefore number many scores. This is also a source of
danger, unless regard be had to the relative fusing points of solders,
and of the parts they unite. (J. G. H.)

BRAZZA, PIERRE PAUL FRANCOIS CAMILLE SAVORGNAN DE, COUNT (1852-1905),
French explorer and administrator, founder of French Congo, was born on
board ship in the harbour of Rio de Janeiro on the 26th of January 1852.
He was of Italian parentage, the family name being de Brazza Savorgnani.
Through the instrumentality of the astronomer Secchi he was sent to the
Jesuit college in Paris, and in 1868 obtained authorization to enter as
a foreigner the marine college at Brest. In the Franco-Prussian War of
1870-71 he took part in the operations of the French fleet. In 1874 when
the warship on which he was serving was in the Gabun, Alfred Marche and
the marquis de Compiegne arrived at Libreville from an expedition in the
lower Ogowe district. Interested in the reports of these travellers, de
Brazza conceived the idea of exploring the Ogowe, which he thought might
prove to be the lower course of the Lualaba, a river then recently
discovered by David Livingstone. Having meantime been naturalized as a
Frenchman, de Brazza in 1875 obtained permission to undertake his
African scheme, and with the naval doctor, Noel Ballay, he explored the
Ogowe river. Penetrating beyond the basin