days the old cumbrous
locomotive, rumbling and puffing along and making only sixty miles
in sixty minutes, is a very dilatory machine in comparison with
our light and beautiful rocket cars, which frequently dart through
the air at the rate of sixty miles in one minute. The advantages
to a country like ours, over 3,000 miles wide, of swift transit
are obvious. The differences in sentiment, politically, nationally,
and morally, which arose aforetime when people under the same
government lived 3,000 miles apart have disappeared to be replaced
by a powerful unanimity that renders possible great social
movements, utterly impossible in the railway age, when seven days
were consumed in journeying from east to west. The old idea that
balloons would be used in this century for travelling has proved
a delusion, almost their only use now being a meteorological one.

Our rocket cars were only perfected in the usual slow course of
invention, and could neither have been constructed nor propelled
a hundred years ago, for neither was the metal of which they are
constructed produced, nor had the method of propulsion or even the
propulsive power been developed. Inventors had to wait till science
had given us in abundance a metal less than a quarter the weight of
iron, but as strong and durable, and this was not until some fifty
years ago when a process was discovered for producing cheaply the
beautiful metal calcium. 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 h