repetitions of the old beaten track through space are by astronomical
incident--but as an epoch _sui generis_, a century _d'elite_, picked
out from the long ranks of time for special service, charged by
Fate with an extraordinary duty, and decorated for its successful
performance. Those of its historic comrades even partially so honored
are few indeed. They will not make a platoon--scarce a corporal's
guard. We should seek them, for instance, in the Periclean age,
when eternal beauty, and something very like eternal truth, gained
a habitation upon earth through the chisel and the pen; in the first
years of the Roman empire, when the whole temperate zone west of China
found itself politically and socially a unit, at rest but for the
labors of peace; and in the sixteenth century, when the area fit for
the support of man was suddenly doubled, when the nominal value of his
possessions was additionally doubled by the mines of Mexico and
Peru, and when his mental implements were in a far greater proportion
multiplied by the press.

[Illustration: CRYSTAL PALACE--LONDON EXHIBITION BUILDING, 1851.]

The last of these periods comes nearest to our standard. The first had
undying brilliance in certain fields, but the scope of its influence
was geographically narrow, and its excessively active thought was not
what we are wont to consider practically productive, its conquests in
the domain of physical science being but slender. The second was in no
sense originative, mankind being occupied, quietly and industriously,
in making themselves comfortable in the pleasant hush after the
secular rattle of spear and shield. The third was certainly full of
results in art, science and the diffusion of intelligence through the
upper and middle strata of society. It might well have celebrated the
first centennial of the discovery of printing or of the discovery of