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MISCELLANEOUS INTELLIGENCE. 



I. Mechanical Science. 



I. Micrometrical Measurement of Saturn, and of Jupiter and its 

 Satellites. — These measurements were made at Dorpat, by M. 

 Striive, with the great achromatic telescope of Fraimhofer, and a 

 micrometer furnished with the threads of a spider's web. By cor- 

 recting^ the relative measures of Saturn and his double ring which 

 were obtained, to the mean distance of that planet, M. Struve brought 

 out the following values in seconds of a degree, and decimals of the 

 second*. 



External diameter of the outer ring 40.215 



Internal diameter 35.395 



External diameter of the inner ring 34.579 



Internal diameter 26.748 



Equatorial diameter of Saturn 18.045 



Width of the outer ring 2.410 



Width of the inner ring 3.915 



Interval between the two rings 0.408 



Interval between the planet and inner ring .... 4.352 

 By combining the observations with certain results given by Bessel, 

 M. Struve deduces that the inclination of the plane of the ring to 

 the ecliptic is 28'. 5'.9, supposing the ring to be of insensible thick- 

 ness, which agrees within 28'. 2 with the result obtained by M. 

 Bessel, with much less powerful instruments. But if Schroter be 

 correct in his supposition, that the ring is 0".125 in thickness, then 

 the inclination will be only 27° 5 5'. 3. 



M. Struve observes, that he has not been able to trace any sub- 

 divisions of the ring. The external ring is sensibly less luminous 

 than the inner ring. The inner ring also appears rather pale on the 

 edge towards the planet, and not so distinctly limited as on the 

 outer edge, circumstances which induce the supposition that the 

 internal edge is less regular than the outer. No distinct spot could 

 be observed on the ring, by which to ascertain its rotation. The 

 five well-known satellites were well observed by the instrument ; 

 the sixth was seen several times ; the seventh, discovered by 

 Herschel, during the disappearance of the ring, never. The fourth 

 presented a small disc, with a diameter of about three-fourths of a 

 second. 



Measurement of Jupiter. — The whole of the observations reduced 

 to the mean distance of the planet, gavet. 



Equatorial diameter of Jupiter. . 38".442 

 Polar diameter 35". 645 



* These angular measurements may be converted into measures of length, 

 by observing, that, at the distance of Saturn, a second of a degree corresponds 

 to about 1600 leagues of 26 to a degree. 



t The second of a degree corresponds, at the distance of Jupiter, to about 

 870 leagues. 



