That
great and enthusiastic, although cautious observer, was the first to sound
the depths of heaven in order to determine the limits and form of the starry
stratum which we inhabit, and he, too, was the first who ventured to throw
the light of investigation upon the relations existing between the position
and distance of remote nebulae and our own portion of the sidereal universe.
William Herschel, as is well expressed in the elegant inscription on his
monument at Upton, broke through the inclosures of heaven ('caelorum
perrupit claustra'), and, like another Columbus, penetrated into an unknown
ocean, from which he beheld coasts and groups of islands, whose true
position it remains for future ages to determine.
Considerations regarding the different intensity of light in stars, and
their relative number, that is to say, their numerical frequency on
telescopic fields of equal magnitude, have led to the assumption of unequal
distances and distribution in space in the strata which they compose. Such
assumptions, in as far as they may lead us to draw the limits of the
individual portions of the universe, can not offer the same degree of
mathematical certainty as that which may be attained in all that
p 88
relates to our solar system, whether we consider the rotation of double
stars with unequal velocity round one common center of gravity, or the
apparent or true movements of all the heavenly bodies.
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