g their flocks by night, could not
but observe the movements of the dog-star, next to the sun the most
brilliant of the luminaries of heaven. They worshipped that star as
a god; and, losing sight of him for about forty days every year,
during his conjunction with the sun, they watched with intense
anxiety for his reaeppearance in the sky, and with that day commenced
their year. By this practice it failed not soon to be found that,
although the reaeppearance of the star for three successive years was
at the end of three hundred and sixty-five days, it would, on the
fourth year, be delayed one day longer; and, after repeated
observation of this phenomenon, they added six hours to the computed
duration of the year, and established the canicular period of four
years, consisting of one thousand four hundred and sixty-one days.
It was not until the days of Julius Caesar that this computation of
time was adopted in the Roman calendar; and fifteen centuries from
that time had elapsed before the yearly celebration of the Christian
paschal festivals, founded upon the Passover of the Levitical law,
revealed the fact that the annual revolution of the earth in her
orbit round the sun is not precisely of three hundred and sixty-five
days and one quarter, but of between eleven and twelve minutes less;
and thus the duration of the year was ascertained, as a measure of
time, to an accuracy of three or four seconds, more or less--a
mistake which would scarcely amount to one day in twenty thousand
years.

"It is, then, to the successive discoveries of persevering
astronomical observation, through a period of fifty centuries, that
we are indebted for a fixed and permanent standard for the
measurement of time. And by the same science has man acquired, so
far as he possesses it, a standard for the measurement of space. A
standard for the measurement of the dimensions and distances of the
fixed stars from ourselves is yet to be found; and, if ever found,
will be through the means of astronomical observation.

"The influence of all these discoveries upon the condition of man is
no doubt infinitely diversified in relative importance; but all,
even the minutest, contribute to the increase and diffusion of
knowledge. There is no richer field of science opened to the
exploration of man in search of knowle