40 



ASTRONOMY. SIR WILLIAM HERSCHEL. 



[Diss. VI. 



his death. 



His impar- Mathematical Sciences, he had to make frequent re- 

 tiality p Or t s on the progress of those progressive branches 

 of knowledge, and to contribute memoirs of the most 

 eminent academicians, both native and foreign. Both 

 these duties he executed with his customary labour 

 and fidelity. His private character was as amiable 

 as his public career was distinguished. The tendency 

 of his writings was constantly to enforce the histori- 



cal credibility of the Scriptures, especially with regard 

 to the most ancient astronomical records. The value 

 of his testimony is increased by his unusual skill in 

 philology. He died 19th August 1822, aged 73. 



We reserve some farther remarks on the geodetic 

 results of this period, and especially on the pendujum 

 observations with which they were accompanied, for 

 the fourth section of this chapter. 



(171.) 



(172.) 

 Sir Wiu. 

 Herschel : 



(173.) 



(174.) 

 early his- 

 tory. 



2. SIR WILLIAM HERSCHEL. History of Sidereal and Telescopic Astronomy to 1820. Her- 

 schel as an Optician. Planet Uranus Solar Spots Orbits of Double Stars Nebulce The 

 Milky Way Sun's Motion in Space. 



The eighteenth century was not, generally speak- 

 ing, distinguished by original observations. The ex- 

 ceptions stand out with all the brighter lustre. 

 Amongst these, the discoveries of Sir William Her- 

 schel occupy perhaps the foremost place. Arago has 

 affirmed that Slough is the spot on the earth's sur- 

 face signalized by the most numerous discoveries, 

 and in a certain sense this is strictly true. No one, 

 before or since (with possibly the exception of Mr 

 Hind) has added so many new bodies to the known 

 planetary system, and this at a time when such 

 discoveries were rarer, more unexpected, and more 

 difficult than now. His researches on the fixed 

 stars are not of a nature to have their importance 

 numerically estimated. 



Sir William Herschel's career was one of the 

 . longest and of the most sustained labour in the history 

 ' of science. To have contributed papers often several 

 in one year to the Philosophical Transactions for 

 thirty-nine consecutive years, from 1780 to 1818, 

 with but two exceptions, is a feat of astonishing per- 

 severance ; but if we recollect that many of these 

 papers contain announcements of capital discoveries, 

 that every one of them is stored with original matter, 

 and that the author had already passed his fortieth 

 year when he commenced the production of this as- 

 tronomical library, we cannot withhold a tribute of 

 the warmest admiration. 



England cannot claim Herschel as her own, except 

 by adoption. He was born at Hanover in 1738, and 

 was one of a numerous family who supported them- 

 selves chiefly by their musical talents. William 

 Herschel, the third son, came to England in 1759 

 with his elder brother, and after struggling with many 

 difficulties, found himself in comparatively comfort- 

 able circumstances as an organist at Bath. In 1774 

 he had executed a reflecting telescope with his own 

 hands, and soon acquired so much dexterity as to 

 construct instruments of ten and twenty feet in focal 



length. In 1780 he contributed his first paper on 

 the variable star in Cetus to the Royal Society, and 

 the following year (13th March 1781) discovered the 

 erratic body, which he at first took for a comet, but 

 which proved to be a planet exterior to Saturn ; the 

 first addition therefore to the number of the primary 

 planets since a period of an immemorial antiquity. 

 So fortunate a success made the name of Herschel 

 speedily famous, and he was effectively befriended by 

 George III., who brought him to IfVe near Windsor, 

 and gave him a pension. 1 



From this brief sketch it will appear how great 

 were the obstacles which Herschel had to vanquish 

 before he became a man of science, and that, besides 

 the claims to distinction already enumerated, his 

 knowledge and his skill were acquired in spite of 

 every disadvantage. 



Practical Astronomy naturally divides itself into 

 two great branches, that which depends upon the 

 use of the telescope merely ; on the telescope and 

 micrometer ; and that which determines the absolute 

 places of the heavenly bodies, and requires the aids 

 of divided instruments and a well furnished obser- 

 vatory. In the century to which he belonged Her- 

 schel is the type of the telescopic observer, Bradley 

 of the instrumental. The discoveries of Aberra- 

 tion and of Nutation by the latter may stand a com- 

 parison with any in the history of science, but the 

 resolution of Nebulae and the proof of the mutual 

 connection of stars in binary systems are not less 

 distinguished and original. Herschel would have 

 gained a great reputation as an optician, merely by 

 the wonderful improvement which he effected in the 

 dimensions and magnifying power of telescopes, and 

 by the skill with which he applied them to celestial 

 observations. He would have stood still higher as 

 an astronomer had he been merely the first observer 

 of a new planet and of eight secondary ones, as well 

 as of several comets, and the author of many nice 



(175.) 



(176.) 

 Division c 

 Practical 

 Astronom; 

 into Tele- 

 scopic and 

 Instru- 

 mental. 



1 It may be doubted whether any other similar annuity was given at that period on scientific grounds alone, and it is difficult 

 to estimate the amount of benefit thus conferred on astronomy, for nothing short of the entire devotion of a lifetime could have 

 produced such results as we owe to Herschel. His proposal to name his planet after the Sovereign was a very natural expression 

 of his gratitude at a period when no rule whatever existed on the subject. See an interesting letter from Herschel to Sir 

 Joseph Banks (who was also a warm friend) in Weld's History of the Royal Society, ii. 146, note. Herschel was elected into the 

 Royal Society 6th Dec. 1781. 



