COMETS. 



123 



principally confined to the Parisians, who seem to be somewhat addicted to such fears. In 

 the year 1773, in consequence of some rumour getting afloat concerning an expected comet, 

 the public tranquillity was completely disturbed, and Lalande was requested by the civil 

 authorities to interfere to assuage the popular terrors. To prevent their renewal in 1832 

 the authority of the Academy of Sciences was invoked in relation to the anticipated 

 visitor, and Arago wrote a celebrated treatise to show the groundlessness of all alarm. 

 Accordingly, the earth's progress in its orbit being at the mean rate of two millions of 

 miles daily, and a month intervening between the passage of the comet across it and the 



arrival of the earth at the same point, the 

 two bodies were never nearer than sixty 

 millions of miles. The accompanying dia 

 gram represents its course as compared with 

 that of the earth. On the ellipse are marked 

 its places for the beginning of each year, 

 from 1833 to 1840. There are 13 elliptic 

 comets now known revolving within the orbit 

 of Saturn ; 7 whose mean distances are 

 nearly equal to that of Uranus; and 21 of 

 long period which pass beyond the limits of 

 the solar system. 



In the spring of 1843 the world was sud 

 denly startled by the apparition of an object 

 in the western heavens, soon after sunset, 

 like a streak of aurora, streaming from the 

 region of the sun below the constellation 

 Orion. Its outline was so distinct, and its 

 light so conspicuous, as immediately to 

 arrest the attention of persons abroad 

 upon the roads, and in vessels at sea. By 

 many observers it was mistaken at first 

 for the zodiacal light ; but its aspect and 

 movements proved it to be a comet of the 

 very largest class. The nucleus was not 

 seen here, but it was visible in more southern latitudes, where the whole appearance of 

 the comet was far more definite than with us. The phenomenon was observed on board 

 the Tay on her homeward voyage from the West Indies, upon the 6th of March ; at 

 Nice on the 12th, by our countryman, Mr. Cooper; at Oporto on the 14th; and at 

 Paris on the 17th. On Sunday evening, soon after seven o'clock, Mr. Cooper had his 

 attention called by his servant to a white line of light near the western horizon. It 

 was like a narrow thin cloud (cirro-stratus), one end being apparently merged in the 

 remaining solar light, and the other in or near the constellation Lepus. On the 13th, 

 at the same hour, the light re-appeared in a direction parallel to the line joining rj 

 Leporis with y Eridani. On the 14th, having prepared his comet-seeker, he found 

 the nucleus by sweeping down the line of light, which appeared stellar about the 

 sixth magnitude. The proportion of the tail actually visible here on the nights of 

 the 17th and 18th was fully 30 in length according to Sir John Herschel, and after 

 ward 45 were measurable by Sir James South. Instead of being luminous at the 

 edges, and more obscure in the middle, a general characteristic of cometary tails, 

 which has induced the belief that they are cones internally empty, the light of the 

 tail, in the present instance, was visibly more intense in the centre than on the sides. 



