ASTRONOMY. 



[NOTES ON COMETS, 



De Vkx>. t Rome, on July 10th. 1846 (1). Discovered 

 by De Vioo, on January 24tli. 1846 (2). Gam hart's or 

 Biela'i comet Discovered by De Vioo, on November 



, IM.'i \t tin* .I;>JH-.IIMIIIV. tin- .-m_;u;.ir pln-iiomi-- 

 non of a double comet was seen. 1846 (3). Discovered 

 by Brorscn, on February 26th. Its elements have some 

 resemblance to the comets of 1532 and 1061. 1846 (4). 

 Discovered by De Vioo, on February 20th. There is no 

 doubt as to the elliptical orbit of this comet, the period 

 being 73 yean. 1846 (5). Discovered by Hind and De 

 Vioo, on July S '<' (6). Discovered by Peters, on 



June 26th. 1H46 (7). Discovered by Brorsen, on April 

 JOth. 1846 (8). Discovered by De Vioo, on December 

 23rd. 1847 (1). Discovered by Hind, on February tith. 

 1847 (2). Discovered by Coller, on May 7th. 1847 (3). 

 Discovered by Schweizer, on August 31st. 1847 (4). 

 Discovered by Man vain, on July 4th. 1847 (5). Dis- 

 covered by Brorsen, on July 20th. 1847 (6). Discovered 

 by Miss Mitchell, on October 1st. 1848 (1). Discovered 

 by Petersen, on August 7th. 1848 (2). Encke's comet. 

 Discovered by Hind, on September 13th. 1849 (1). Dis- 

 covered by Petersen, on October 26th, 1848. 1849 (2). 

 Discovered by Oonjon, on April 15th. 1849 (3). Dis- 

 covered by Schweizer, on April llth. 1849 (4). Dis- 

 covered by Mr. Jenkins, on November 28th, at sea. 

 1850 (1). Discovered by Petersen, on May 1st 1850 (2). 

 Discovered by Bond, on August 29th. 



1851 (1). Faye's comet. Discovered at the Cambridge 

 Observatory, on November 28th I860. ] 851 (2). Dis- 

 covered by D' Arrest, on June 28th. 1851 (3). Discovered 

 by Brorsen, on August 1st. 1851 (4). Discovered by 

 Brorsen, on October 22nd. 



[Omitting various minor cometary appearances, we 

 may give a short description of two remarkable comets, 

 which appeared in 1858 and 1801. 



On June 2nd, 1858, M. Donati discovered the comet 

 which has since borne his name. Until August 23rd, it 

 .did not present any marked appearance to observers in 

 'this kingdom, but was a round, bright object, like a 

 .nebulous patch of light, with a condensed centre, and 

 without a tail. It was not visible to the naked eye till 

 : September, when it suddenly presented a most magnifi- 

 cent appearance. On October 5th, it passed near Arc- 

 t iinn, its tail being very brilliant, and of a length of full 

 .40, through which 'bright stars could be easily dis- 

 tinguished. The -appearance of the tail continually 

 varied. We.pbserved it about the beginning of October, 

 : at Campbelton, in Argylehire, where the clearness of the 

 .air wag extremely favourable, and, on one evening, a 

 .curious contrast was presented to it by the display of a 

 brilliant auiora borealis, which it however exceeded in 

 brightness. Its periodic. time has been calculated to be 



2,100 years. It was, at first, supposed to be the return 

 <>f the comet of 1550, but 117. 



element* showed such an 

 opinion to be erroneous. 

 The annexed cut will give an 

 idea of its general appear- 

 ance at the commencement 

 of October, as seen and sketch- 

 ed at the time. 



In the latter portion of 

 June, 1861, every one was 

 startled by the sudden ap- 

 pearance of a comet, at dusk, 

 on Sundayevening, June 30th. 

 The writer observed it, before 

 sunset, as a kind of nebu- 

 lous patch, mistaking it for a star liiil by haze. But, 

 about eleven o'clock, all clouds having cleared away 

 from the south-eastern sky, a in i, r ni!iivnt coiiu-t, with a 

 bright nucleus, and a tail of nearly 00 in length, pre- 

 sented itself. Its image was distinctly reflected from the 

 sea (Ramsgate pier being the point of our observat 

 The tail had a quivering motion, very much resembling 

 that of the streamers of the fig. us. 



aurora borealis, and was divided 

 near the head into two parts. 



The annexed cut gives an 

 Idea of its appearance, 

 also, folio plate, page '.CC). 



It was calculated, on June 

 25th, by Professor Challis, of 

 Cambridge, that the comet was 

 distant 82 millions of miles 

 from the sun. And that its 

 tail had a length of 10 millions 

 of miles. Its brightness rapidly 

 diminished as it receded from 

 the sun ; and, on August 24th, 

 its distance from that body was 

 about 140 millions of miles, in- 

 creasing, in a week, to 152 mil- 

 lions, by which time it had ar- 

 rived in the northern part of the constellation Bootes. Its 

 tail had almost disappeared by this date, and in a few days 

 powerful telescopes failed to discover it. 



The most remarkable fact respecting this comet was its 

 sudden appearance. It hail not been sivu by any of the 

 observatories in Europe, till it so suddenly burst on the 

 eye, of a size which was its maximum. For three days, 

 however, previously to its discovery, the weather had 

 been very cloudy, and the sky almost entirely overcast. ] 

 EDITOR. 



CHAPTER IX. 

 ECLIPSES AND OCCULTATIONS. 



TH striking phenomena attending eclipses of the sun 

 and moon, in which, apparently, the course of nature is 

 interrupted, and for a time the discs of the sun and full 

 moon lone their wonted lustre, and their light is almo it 

 extinguished in the mid-heavens, have ever been a source 

 of curiosity, and occasionally of terror, to mankiii 1. 

 WhiUt they have furnished many examples of credulity 

 uhirh have been taken advantage of by superior minds, 

 they have sometimes served a nobler purpose ; and the 

 biography of astronomers is filled with instances in wl i id i 

 the accidental occurrence of a solar or lunar eclipse, 

 has been the cause of their first directing attention to 

 the Kit-nee that ha* been subsequently i-n:i<li,.i by their 

 investigation*. Eelijuet may ba defined as a short inter- 

 ni;-.i .11 in the passage of light to the earth, which is 

 either mil, a* in the case of the interposition of an 

 opaque body between the earth and sun ; or apparent, as 

 Ukm plaoa when the earth iUelf passes between tho tun 

 Ail the object previously illuminod. Tno drst are 



termed solar eclipses, ami take place at tho time of the 

 new moon ; the latter are lunar ixlipsi-s, and occur at the 

 time of full nvran, or when the earth is interposed be- 

 tween the sun and her satellite ; thu earth being a 1 

 of such dimensions that its shadow is sufficient to reach 

 to the moon. 



LUN.VK Kri.ir.sKs. Taking the latter case, or that of 

 a lunar eclipse, we readily see by Fig. 119 this form of the 

 shadow cast by the earth. The suu, S, .scatters its rays 



Fig. lit. 



m aU directions, an 1 such as are diroetod towards the 

 eirt\ T,'will ba interrupted iu th^ir on war. I p.i<sa-. by 



