Miscellanies. 207 



8. Guile's Three Comets. — Mr. Galle, assistant observer at the 

 Royal Observatory of Berlin, has discovered three comets in the short 

 space of three months. 



The ^rs^ was discovered Dec. 2, 1839 ; it passed its perihelion Jan. 

 4, 1840, and was visible to the naked eye for a few nights in January 

 as a nebulous star of the iifth magnitude. 



The second comet Avas discovered Jan. 25, 1840; it passed its per- 

 ihelion March 12, 1840. It was seen at several places in the United 

 States, without, however, being visible to the naked eye. 



These two comets are considered as new discoveries. Their ele- 

 ments do not agree with those of any that have yet been observed. 

 Their motions may be perfectly represented by supposing them to 

 move in a parabola, a curve which does not return into itself: so that 

 no plausible conjectui-e can be formed respecting the time of their 

 past or future appearances, except that the period of their revolutions 

 cannot be much short of a thousand years. 



The third comet was discovered March 6, 1840; it passed its peri- 

 helion April 2, 1840 ; its tail (visible only in a telescope) might be 

 traced through several degrees. Its elements, compared by its dis- 

 coverer in connection with Encke, show that it is the same as that 

 which appeared in 1097 and 1468, and that its period is about 370 

 years. Its two last appearances occurred in the autumn, when it 

 passed much nearer the earth, and hence its greater brilliancy. — Jour. 

 of Franklin Institute, May, 1840, p. 358. 



9. New Comet. — The third comet of A. D. 1840, was discovered at 

 Berlin, Oct. 26, 1840, by Dr. Bremicker. It was then near o Draconis, 

 and appeared as a faint nebula. Its elements, as computed by Mr. Peter- 

 sen, Assistant Observer at the Altona Observatory, from observations 

 taken Oct. 27, 28 and 31, are as follows : 



Passage of Perihelion, 1840, Nov. 15.9154, m. t. Altona. 



Perihelion distance, - - . . 1.44805 



Longitude of Perihelion, - - - 25° 17' 



" Ascending Node, - - 248° 31' 55" 



Inclination, 57° 29' 50 " 



Motion direct. 



Astr. Nachr. 412, quoted by S. C. Walker, Esq. in Phil. Nat. Gaz. 

 Dec. 24, 1840. 



10. Manufacture of Glass for Optical Instruments. 

 To the Editors of the American Journal of Science and Arts. 

 Gentlemen, — Glass is a well known substance, which has been 

 made and used from remote antiquity, and the manufacture, like most 



