SCIENTIFIC SUMMARY. 
437 
being uncovered traces of Indian workings were found. Two specimens 
were cut off, which were shown to be very compact pure copper. One 
of the masses found was forty feet in length by four in breadth, and 
weighed about fifty tons. 
Native Silver. — No one would think of mining for silver in the stomach 
of a mule, yet in the Geological Museum there is a lump of silver “about 
as much as would make forty shillings,” which has been taken from such 
a locality. It appears to be a common occurrence to find quantities of 
silver in the stomach and intestines of mules working in the Mexican 
silver mines, and its presence is accounted for by the mules eating mud, 
which contains much silver, for the purpose of obtaining the salt which is 
also mixed up with it. The silver is said to accumulate to a considerable 
extent without proving injurious. 
METALLURGY. 
The Dowlais Iron Works. — In our last number we stated that the 
weekly make of iron is 130 tons. It should have been added, that this is 
the produce of each of the eighteen furnaces possessed by that establish- 
ment. At present it appears to be about 150 tons per furnace, or about 
2700 tons weekly for the whole establishment. In many districts the 
weekly make of iron per furnace varies from 250 to 300 tons. 
Aluminium. — This metal has risen suddenly to a position of great 
importance. Although isolated by Sir Humphrey Davy, and obtained in 
globules by Wohler in 1845, it was not prepared in any quantity, until 
within the last few years, when Deville’s improvements led to its being 
produced in considerable masses. Messrs. Bell, of Newcastle-on- Tyne, 
now manufacture it largely by Deville’s process, which essentially consists 
in the decomposition of dry chloride of aluminium by means of sodium. 
The metal was exhibited by this firm, and by Messrs. Morin & Co., of 
Nanterre (Seine), at the late International Exhibition, under the form of 
bars, wire, sheets, tubes, foil, castings, and forgings. It has been drawn 
into wire by M. Garepou, of Paris, and it is said to be from 60 to 100 per 
cent, cheaper than silver wire. It is exceedingly light (its specific gravity 
being little more than 2 - 5) ; thus, a sextant in brass will weigh 3 lb., which, 
if made of aluminium, weighs only 1 lb. 9 oz. Such a sextant, and also 
various other philosophical instruments of the same material, were ex- 
hibited by Messrs. Bell. They have recently produced a modification, 
which they term “ whitened aluminium,” in which the unpleasant zinc- 
like hue of the metal is obviated. They have also formed keys of alumi- 
nium, alloyed with 2 per cent of nickel, to increase its hardness. From 
aluminium wire and foil the lighter weights used for chemical purposes 
may be advantageously made, since, occupying something like seven times 
the space of those of platinum, they are more easily adjusted and handled, 
and less likely to be lost. MM. Collett, of Paris, have constructed a chemical 
balance, in which every part, down to the milled head by which the beam 
is released, is made of aluminium. It would appear, however, that this 
metal is destined to be more useful as a constituent of alloys, than in the 
unalloyed form. 
