CHAPTER V.
THE CONSTRUCTION OF THE HEAVENS.
"A Knowledge of the construction of the heavens," Herschel wrote in 1811, "has always been the ultimate object of my observations." All his other investigations—solar, planetary and stellar—were secondary to this great aim. Before the commencement of his career as an astronomer, the stars attracted very little attention. Star-catalogues had been formed, but, nevertheless, the stars were regarded chiefly as convenient reference-points for observations of the Moon and planets. A few double and variable stars and several star-clusters and nebulae had been discovered; theories of stellar distribution had been outlined by one or two obscure non-professional astronomers, such as Wright and Lambert. But there was little interest among astronomers in the study of the stars for their own sakes; and no great systematic effort had been made to discover the laws of stellar distribution and motion.
The field of sidereal astronomy, therefore, was virtually untrodden when, shortly after the beginning of his telescopic work, Herschel began his first review of the heavens. His second review, commenced in 1779, included stars down to the eighth magnitude. By-products of this review were the discovery of Uranus and the formation of his first catalogue of double stars. In December, 1781, he commenced his third review, which he completed in January, 1784, and which resulted in the publication of a second double-star catalogue. The prob-
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