iodide of starch at a high temperature. He
shows that the iodide may resist heat, and that the loss of color depends
on the greater attraction of water for iodine as compared with starch, and
the greater solubility of iodine in water at high temperatures.

The different kinds of starch do not take the same tint with the same
quantity of (solid) iodine. That from the potato _arum_ gives a blue, and
that from wheat and rice a violet tint; while the filtrate from starch
paste, from whatever source, always gives a blue color.

* * * * *

THE AMALGAMATION OF SILVER ORES.

DESCRIPTION OF THE FRANCKE "TINA" OR VAT PROCESS FOR THE AMALGAMATION OF
SILVER ORES.

[Footnote: Paper read before the Institution of Mechanical Engineers at
the Cardiff meeting.--_Engineering_.]

By Mr. EDGAR P. RATHBONE, of London.

In the year 1882, while on a visit to some of the great silver mines in
Bolivia, an opportunity was afforded the writer of inspecting a new and
successful process for the treatment of silver ores, the invention of Herr
Francke, a German gentleman long resident in Bolivia, whose acquaintance
the writer had also the pleasure of making. After many years of tedious
working devoted to experiments bearing on the metallurgical treatment of
rich but refractory silver ores, the inventor has successfully introduced
the process of which it is proposed in this paper to give a description,
and which has, by its satisfactory working, entirely eclipsed all other
plans hitherto tried in Bolivia, Peru, and Chili. The Francke "tina"
process is based on the same metallurgical principles as the system
described by Alonzo Barba in 1640, and also on those introduced into the
States in more recent times under the name of the Washoe process.[1]

[Footnote 1: Transactions of the American Institute of Mining Engineers,
vol. ii., p. 159.]

It was only after a long and careful study of these two processes, and by
making close observations and experiments on other plans, which had up to
that time been tried with more or less success in Bolivia, Peru, and
Chili--such as the Mexican amalgamation process, technically known as the
"patio" process; the improved Freiberg barrel amalgamation process; as
used at Copiapo; and the "Kronke" process--that Herr Francke eventually
succeeded in devising his new process, and by its means treating
economically the rich but refractory silver ores, such as those found at
th