▼OL. XTI.] FHILOSOPHICAL TRANSACTIOKS. 363 



The Theory of the Jive Satellites of Saturn corrected. By M. Cassini. N° 187, 

 p, 299. Translated from the French. 



The distance of the first satellite of Saturn from his centre appeared variable, 

 and its motion sensibly unequal, being swifter in the western semicircle than in 

 the eastern. At length M. Cassini determined its mean distance at W of the 

 diameter of Saturn's ring, and its diurnal motion at 6' 10° 41' 31". So that, if 

 its motion were uniform, the duration of its conjunction with Saturn, that is, 

 the whole time of passing over his ring, would be ^\^. 46m.; but by observa- 

 tion it has appeared greater. He calculated the epoch of its motion Dec. 31, 

 1685, at noon, for the meridian of Paris, in Capricorn 24° 50'. 



The distance of the second satellite from the centre of Saturn appeared more 

 uniform, which he determined at a diameter and a quarter of the ring. Its 

 motion also appeared more equal; and its diurnal motion he calculated at 4" 1 1° 

 31' 30": so that the duration of its conjunction would be 8h. 36m. He could 

 never observe this satellite approach nearer the planet's ring than \ of an ansa. 

 And as this satellite is for the most part to be seen within the confines of the 

 distance of the first, to which it is equal in magnitude, and alike in colour, it 

 proved a very difficult matter to distinguish them. The epoch of this planet, 

 for the noon of Dec. 31, l685, he determined, in Virgo 9° 10'. 



The distance of the 3d satellite from the centre of Saturn appeared to be 1^ 

 of the diameter of the ring. Its diurnal motion was 2' 18° 41' 50". So that 

 its conjunction ought to last for 10 hours. And the epoch of its motion for 

 the noon of Dec. 31, l685, was in Virgo 9° 39'. 



The distance of the fourth satellite from Saturn's centre was 4 diameters of the 

 ring. Its diurnal motion 22° 34' 38"; the duration of its conjunction 15h. 

 6m.; and the epoch of its motion, for the same time and place as the others 

 in Pisces 18° l'. 



The distance of the 5th satellite from the centre of Saturn, was 12 diameters 

 of his ring; its diurnal motion 4° 32' 17"; its conjunctions continue for 24 

 hours; and the epoch for the same time and place as above, in Pisces l6° 19'. 

 From which principles may tables and ephemerides be constructed. 



Observations and Experiments concerning the Growth of Trees. By Thomas 

 Brotherton, of Hey, in the County of Lancaster, Esq. Communicated by 

 R.H. F. R. S. N° 187, p. 307. 



A crab tree, about 4 inches in diameter, was hacked round with a hatchet, 

 so as to cut pretty deep into the wood, besides cutting off the bark, for about 



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