--How same can be hardened and still retain its
color? The following are formulas for white metal. Melt together: (a)
Tin 82, lead 18, antimony 5, zinc 1, copper 4 parts. (b) Brass 32,
lead 2, tin 2, zinc 1 part. For a hard metal, not so white, melt
together bismuth 6 parts, zinc 3 parts, lead 13 parts. Or use type
metal--lead 3 to 7 parts, antimony 1 part.
What Metal Expands Most, for the Same Change in Temperature?--For one
degree Centigrade the following are coefficients of linear expansion:
aluminum, 0.0000222; silver, 0.0000191 to 0.0000212; nickel,
0.0000128; copper, 0.0000167 to 0.0000178; zinc, 0.0000220 to
0.0000292; brass, 0.0000178 to 0.0000193; platinum, 0.0000088.
Heavy Timbers.--There are sixteen species of trees in America, whose
perfectly dry wood will sink in water. The heaviest of these is the
black iron wood (confalia feriea) of Southern Florida, which is more
than 30 per cent. heavier than water. Of the others, the best known
are lignum vitae (gualacum sanctum) and mangrove (chizphora mangle).
Another is a small oak (quercus gsisea) found in the mountains of
Texas, Southern New Mexico and Arizona, and westward to the Colorado
desert, at an elevation of 5,000 to 10,000 feet. All the species in
which the wood is heavier than water belong to semi-tropical Florida
or the arid interior Pacific region.
Highest Point Reached by Man was by balloon 27,000 feet. Travelers
have rarely exceeded 20,000 feet, at which point the air from its
rarity is very debilitating.
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