n8 KANT'S UNIVERSAL NATURAL HISTORY 



it from the velocity of one of the satellites of Saturn, by 

 taking the same as standing in the ratio of the square 

 root of the distances from the centre of the planet. The 

 velocity thus found immediately gives the time for the 

 rotation of Saturn round its axis : it is six hours, twenty- 

 three, minutes, and fifty-three seconds. This mathematical 

 calculation of the unknown movement of a heavenly body, 

 which is perhaps the only prediction of its kind in natural 

 science proper, awaits verification by the observations of 

 future times. The telescopes yet known in our time do 

 not magnify Saturn so much that the spots which may 

 be supposed to exist on its surface, could be discovered 

 by them so as to make out by their displacement its 

 rotation around its axis. But telescopes have perhaps not 

 yet attained all that perfection which may be hoped for, 

 and which the industry and dexterity of the mechanicians 

 appear to promise. If the day should ever come when 

 our conjectures would be verified by actual inspection, 

 what certainty would not our theory of Saturn thereby 

 acquire and what pre-eminent credibility would not be 

 gained for the whole of our system which is founded 

 upon the same principles? 1 The period of the diurnal 

 rotation of Saturn also yields the ratio of the centrifugal 

 force of its equator to the gravitation upon its surface ;- 

 the former is to the latter as 20 : 32. The gravitation is 

 therefore only about f ths greater than the centrifugal force. 

 This comparatively large ratio necessarily causes a very 

 considerable difference between the diameters of this 

 planet ; and one might suspect that it must turn out so 

 great that observation of this planet, although but little 



1 From telescopic observation the time of rotation is now given as. 

 about 10 hours, 14 minutes, 24 seconds. Tr. 



