But calcium would have been little use
alone. Aluminium, which is now so plentiful, had to be alloyed
with it, and aluminium was not used to any great extent till the
beginning of this century, when an electric process of reducing it
quickly from its ore--common clay--was discovered. The metal known
as calcium bronze, which is now so common, is an alloy of calcium,
0.75; aluminium, 0.20; and 0.05 of other metals and metalloids in
varying proportions according to different patents. This alloy has
all the useful properties of the finest steel with about one-fourth
its weight, and is besides perfectly non-oxydisable and never
tarnishes. Without the production of a metal with all these
combined qualities, we might still in our journeys, be dawdling
along at sixty miles an hour in a cumbrous railroad car behind
a snorting, screaming locomotive.
Our swiftly darting cars were not at first constructed on such
perfect principles as now. Invention seems to follow certain laws,
and has to take its time. A new discovery in physics has to be
supplemented by one in chemistry, and one in chemistry by another
in physics, and so on through a whole century, perhaps, before any
great invention is perfected. Thus it happens that, though the
principle of the rocket has been known for an age, it is only
comparatively recently that it has been applied to the propulsion
of cars.
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