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At the close of the eighteenth century Herschel, armed with a powerful
telescope, considerably reduced the preceding measurements.
He assigned a height of 11,400 feet to the maximum elevations,
and reduced the mean of the different altitudes to little more
than 2,400 feet. But Herschel's calculations were in their turn
corrected by the observations of Halley, Nasmyth, Bianchini,
Gruithuysen, and others; but it was reserved for the labors of
Boeer and Maedler finally to solve the question. They succeeded
in measuring 1,905 different elevations, of which six exceed
15,000 feet, and twenty-two exceed 14,400 feet. The highest
summit of all towers to a height of 22,606 feet above the surface
of the lunar disc. At the same period the examination of the moon
was completed. She appeared completely riddled with craters, and
her essentially volcanic character was apparent at each observation.
By the absence of refraction in the rays of the planets occulted
by her we conclude that she is absolutely devoid of an atmosphere.
The absence of air entails the absence of water. It became,
therefore, manifest that the Selenites, to support life under
such conditions, must possess a special organization of their
own, must differ remarkably from the inhabitants of the earth.
At length, thanks to modern art, instruments of still higher
perfection searched the moon without intermission, not leaving
a single point of her surface unexplored; and notwithstanding
that her diameter measures 2,150 miles, her surface equals the
one-fifteenth part of that of our globe, and her bulk the
one-forty-ninth part of that of the terrestrial spheroid-- not
one of her secrets was able to escape the eyes of the
astronomers; and these skillful men of science carried to an
even greater degree their prodigious observations.
Thus they remarked that, during full moon, the disc appeared
scored in certain parts with white lines; and, during the
phases, with black. On prosecuting the study of these with
still greater precision, they succeeded in obtaining an exact
account of the nature of these lines. They were long and narrow
furrows sunk between parallel ridges, bordering generally upon
the edges of the craters. Their length varied between ten and 100
miles, and their width was about 1,600 yards. Astronomers called
them chasms, but they could not get any further. Whether these
chasms were the dried-up beds of ancient rivers or not they were
unable thoroughly to ascertain.
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