124 PROGRESS IN ASTRONOMY. 



To do this, of course, great optical power was necessar}^ and such 

 was his energy that, as large instruments were not to be obtained at 

 any price, he set to work and made them himself. 



Herschel presented the beginning of the nineteenth centur^' not only 

 with a delinite idea of the constitution of the stellar S3\stem, based on 

 a connected body of facts and deductions from facts, as gleaned through 

 his telescopes, but observations without number in many lields. He 

 discovered a new planet, Uranus, and several satellites of the planets; 

 published catalogues of nebulae; established the gravitational bond 

 between many "double stars;" and carried on observations of the sun, 

 then supposed to be a habitable globe. What Herschel did for obser- 

 vational astrononi}^ and deductions therefrom Laplace did for the fur- 

 therance of our knowledge concerning the exact motions of the bodies 

 comprising the solar system. Newton had long before announced that 

 gravitation was universal, and Laplace brought together investigations 

 undertaken to determine the validity of this law. These were given 

 to the world in his wonderful book on "Celestial Mechanics," the first 

 volumes of which appeared in 1799. 



A survey of the work of these two great astronomers gives one an 

 idea of what was going on in observational and mathematical astron- 

 omy at the beginning of the century. 



The study was now destined to make rapid strides, as not only were 

 new optical instruments, some designed for special purposes, intro- 

 duced, new mathematical processes applied, fresh fields for research 

 opened up, but the number of workers was considerably augmented by 

 the increased means available; so much so, indeed, that the first astro- 

 nomical periodical was founded by Von Zach in 1800 to facilitate inter- 

 communications between the observers. 



The first evening of the nineteenth century (January 1, 1801) augured 

 well for progress. It had long been thought that all the members of 

 the solar S3'stem had not as yet been discovered, and there was a very 

 notable gap between the planets Mars and Jupiter, indicated by Bode's 

 law. Observers were organized to make a thorough search for the 

 missing planet, portions of the sky being divided between them for 

 minute examination. It fell to the Italian observer, Piazzi, to discover 

 a small body which was moving in an orbit between these two planets, 

 on the date named. The century thus began with a sensation, and, 

 because the new body, which was named "Ceres," was notof sufiicient 

 size to be accepted as the "missing planet," the idea was suggested 

 that perhaps it was a fragment of a larger planet that had been blown 

 to pieces in the past. 



An opportunity here arose for mathematical astronomy to come to 

 the help of the observer, for Ceres soon was lost in the solar rays, and 

 in order to rediscover it after it had passed conjunction an approxi- 

 mate knowledge of its path and future position was necessary. 



