. Discovery. Science. 6 IJISCOVERY "A knowledge of the construction of the heavens," he wrote in 1811, " has always been the ultimate object of my ; In 1784, in his first paper on the subject, he described his method of star-gauging, which, he said, " consists in repeatedly taking the number of stars in ten fields of view of my reflector very near each other, and by adding their sums and cutting off one decimal on the right, a mean of the contents of the heavens, in all the parts which are thus gauged, is ; In 1785 Herschel outlined his the
. Discovery. Science. 6 IJISCOVERY "A knowledge of the construction of the heavens," he wrote in 1811, " has always been the ultimate object of my ; In 1784, in his first paper on the subject, he described his method of star-gauging, which, he said, " consists in repeatedly taking the number of stars in ten fields of view of my reflector very near each other, and by adding their sums and cutting off one decimal on the right, a mean of the contents of the heavens, in all the parts which are thus gauged, is ; In 1785 Herschel outlined his theory of the universe. " That the Milky Way," he said, " is a most extensive stratum of stars of various sizes admits no Innpcr of the least doubt, and. SIR W. By kind pcrmii^ioii ul Ihc '. that our sun is actually one of the heavenly bodies belonging to it is ; The distant nebute were looked upon as external universes, and in 1785 he remarked that he had discovered 1,500 universes. Herschel made two important assumptions—that his gauging telescope was sufficiently powerful to penetrate to the limits of this stratum, and that the stars were distributed with some approach to uniformity. Ob- viously, if these assumptions are granted, the number of stars in any given region of the heavens becomes a criterion of the depth of the stratum in that direction. Herschel was thus enabled to estimate the possible dimensions and shape of the sidereal system. He sketched it as a cloven disc of irregular outline, extend- ing much farther in the direction of the Milky Way or Galaxy than in that of the galactic pwles, the cleft re- presenting the division in the galactic stream. The sun he believed to be almost, but not quite, centrally placed, being slightly nearer to the north galactic pole than to the south, and perceptibly closer to the boundaries of the system in the direction of Cania Major than of Aquila. On the disc-theory, then, the sider
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