SIR JOHN FREDERICK WILLIAM IIERSCHEL, 119 



Soutlieni Hemisphere, conipielieiKling- 1.015, Avas reduced, arranged, aud 

 executed by Sir John's own hand.s, and appears Mke tlie work of a life- 

 time. 



In treating- of the MageUanic clouds, two line eye-sketches are given, 

 ^' drawn without telescopic aid, when sealed at a table in the open air, 

 in the absence of the moon, and with no more light than was absolutely 

 necessary for executing a drawing at all." He was compelled to this 

 method in consequence of his attempts to represent other than very 

 small portions of the KuhecuJa Major m the telescoi)e, having been com- 

 pletely baffled by the perplexity of its details. 



On the 25th of October, 1837, Sir John was fortunate enough to ob- 

 tain a view of the anxiously expected comet of Dr. Ualley. In the fifth 

 chapter of the " Astronomical Observations'' he has given the results of 

 his notice of this singular member of our solar system. Thirteen draw- 

 ings illustrate the comet. We have it as it appeared night after uigbt. 

 On the 1st of Xovember he describes its nucleus as small, bright, and 

 highly condensed, shielded on the side next the sun by a narrow cres- 

 cent of vivid, nebulous light, tlie front presenting an outline nearly cir- 

 cular, and having an amplitude of 0(P from horn to horn. Four days 

 afterward it had the common appearance of a comet, with its nucleus and 

 slightly diverging tail ; but on its return from th(^ sun, on the 2Gth of 

 January, it assumed a new and sur])rising ai)pearance. Its head was 

 sharply terminated " likeaground-glass lamp-shade, and within thishead 

 was seen a vividly luminous nucleus, as if a miniature comet, i^erfect in 

 itself, possessing head and tail, and considerably exceeding the surround- 

 ing head in intensity of light ;" in fact, a comet within a comet. As the 

 nights followed each other, and the stranger advanced across the heav- 

 ens, its increase in dimensions was so rapid "that it might be said it 

 Avas almost seen to grow." On the 20th the nucleus appeared as a star 

 of the tenth magnitude, furred and nel)ulous, and more than double in 

 size within twenty-four hours. On the 2Sth, npon looking through the 

 20-foot reflector, Sir John exclaimed, "Most astonisliing! The coma is all 

 but gone, and there are long irregular tails everywhere.''' Tlie nucleus 

 was then a sharp point, like one of Jujnter's satellites in a thick fog of 

 hazy light — no well defined disk could be raised njmn it — and its bod^' 

 was clearh- discernable from its coum. " I can hardly doubt," he writes, 

 " that this comet was fairly evaporated in perihelio by the sun's heat, 

 resolved iuto transparent vapor, and is now in pro(!ess of rapid conden- 

 sation aud reprecii)itation on the nucleus." 



Sir John concludes his "astronomical observations" by notices of 

 the solar spots, and conjectures of their causes. Thirteen figures, delin- 

 eated from magnified images formed on a screen by means of a 7-foot 

 achromatic refractor, are given in a single plate. One of these spots 

 occupied an area equal to 3,780,000,000 square miles. Of one huge spot 

 he makes no measurement. Of another, not one tenth in size, he says, 

 "Its black center would have allowed the globe of our earth to drop 



