374 Miscellanies. 



by 1, 2, 4, 8, 16, . . . 64. There seems to be a blank between the sixth 

 and seventh ; to be filled perhaps by the discovery of a new satellite ; 

 as Avas the apparent hiatus between Mars and Jupiter by the four tel- 

 escopic planets. 



Table of the approximate dimensions of Saturn and of his rings. 



French leagues. 

 Equatorial diameter of the planet, - - 28,664 



Interval between Saturn and interior ring, - 6,912 



Internal diameter of do. - 42,488 



Diameter of first division, ... 45,468 



second, .... 49,720 



third, .... 52,806 ? 



External diameter of interior ring, - - 54,926 



Interval between the two rings, ... 648 ? 



Internal diameter of the exterior ring, - - 56,223 



Diameter of the fourth division, - . - 60,286 



External diameter of the exterior ring, - - 63,880 



Thickness of ring, according to Herschel, - 36 ? 



Comptes Renins Acad. Sci. Sept. 24, 1838, p. 658, 9. 



It will be remembered that several divisions in Saturn's ring have 

 long been suspected and occasionally set-n, as by Cassini, Short, 

 Quetelet, and Kater ; but the evidence hitherto brought forward is 

 far less satisfactory than that above recorded. 



51. Solar Painting-. — The barbarous term, Daguerrotype, inven- 

 ted to commemorate M. Daguerre, the discoverer of the improved 

 method of copying figures by the sun's light, denotes the instrument 

 by which this beautiful result is obtained. 



M. Arago has recently revealed the secret to the French Institute 

 at Paris. We omit his recapitulation of the rise and progress of dis- 

 covery in regard to the effect of the sun's rays on colors, and also the 

 more appropriate notice of the labors of M. Niepce, who preceded M. 

 Daguerre in the research. 



The following is the account of the process of M. Daguerre : — A 

 copper sheet, plated with silver, well cleaned with diluted nitric acid, 

 is exposed to the vapor of iodine, to form the first coating, which 

 is very thin, as it does not exceed the millionth part of a millimetre in 

 thickness. There are certain indispensable precautions necessary to 

 render this coating uniform, the chief of which is the using of a rim 

 of metal round the shee-t. The sheet thus prepared, is placed in tlie 

 camera obscura, where it is allowed to remain from eight to ten min- 

 utes. It is then taken out, but the most experienced eye can scarcely 



