MODERN SCIENCE. 211 



by the telescopic power we possess. As regards the others, 

 photography has confirmed the views of the Herschels they 

 are vast masses of luminous gases, which time and cooling 

 will contract into planetary systems in accordance with 

 Laplace's theory. John Herschel's famous Outlines of 

 Astronomy (1838), treated as Arago had already done in 

 France (Astronomic Populaire 1834), is the earliest and 

 finest work it is possible to read in the English language on 

 the subject. For the first time was the general reader put in 

 a position to understand the wonders of the heavens : it is, in 

 point of clearness, simplicity, and eloquence, on a par with 

 Arago's work. As a physicist, John Herschel's treatises on 

 Sound and Light are valuable contributions to science. He 

 carried on, together with Talbot and Brewster, a series of 

 experiments on light and the colours of burning substances, 

 and suggested, like Talbot, to make the flame-colours a 

 means of chemical analysis (1822). He IMPROVED THE 

 SPECTROSCOPE in collaboration with J. Browning (1870). 

 Herschel may be said to have founded practical mineralogy : 

 he was no stranger to any of the physical sciences, and it 

 is not too much to say that they are all indebted to him in 

 one way or another. As an instance of his scientific 

 universality, we may take his determination of the relative 

 luminosity of heavenly bodies. Wollaston had ascertained 

 that the full moon gives 801,072 times less light than the 

 sun; Herschel determined that the light of the full moon 

 exceeds that of a Centauri 27,408 times ; so that ff the ratio 

 between sunlight and starlight would be that of 22,000 millions 

 to one." 



1811 1877. Leverrier, concurrently with Adams, after 

 calculating the deviation of Uranus from its orbit, ascribed 

 this perturbation to be due to the presence of an unknown 

 body external to Uranus, and this proved to be the case ; 

 for (Berlin) astronomers, instructed by precise directions from 

 Leverrier as to the region where the planet was to be looked 

 for, discovered NEPTUNE on the same night (September 23, 

 1846), the orbit of which is thirty times more remote from 

 the sun than ours. This feat, which may be regarded as 

 one of the greatest triumphs yet achieved by Newtonian 



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