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LXVIII. Notices respecting New Books. 



The Meteoric Theory of Saturn s Rings considered with reference to 

 the Solar Motion in Space, also a paper on the Meteoric Theory of 

 the Sun. By Lieut. Augustus Morse Davies, B.A., R.A., Sfc. 

 Longmans, 1871. 



HPHIS work, illustrated by nineteen plates, is, as its title imports, 

 -*- nearly pure theory. Based upon the assumption, which the 

 author considers he is justified " in making of the solar motion being 

 in reality a curve," he builds up his theory of the rings of Saturn 

 having resulted from the planet arresting groups of meteors which 

 it encountered as they descended towards the sun. 



The work is divided into sections, the first containing brief notices 

 of the successive theories which have been broached from the time 

 of Maupertius to that of Proctor, three hypotheses having been sub- 

 mitted, viz. the solid, the fluid, and the satellitic. In connexion 

 with the last, Lieut. Davies has the following remark : — " I have 

 thus far attempted to sketch very briefly the satellite theory of 

 Saturn's rings ; and here the question naturally arises, Whence has 

 this vast cloud of minute satellites been drawn, and how has it been 

 subjected to Saturn's dominion ? Has Saturn always been attended 

 by these magnificent rings, or has some fortuitous encounter with 

 space-wandering meteors enabled it, at some remote period, to enrich 

 the splendour of its eight-mooned orb ? " The remaining portion of 

 the section is occupied with considerations tending to show that, of 

 the four large and exterior planets, Saturn is more favourably situ- 

 ated for arresting and retaining groups of meteors than either Jupiter, 

 Uranus, or Neptune. 



In Section II. Lieut. Davies proceeds to determine the absolute 

 path of Saturn in space upon the assumption of the solar curve, and 

 chooses for the epoch that in which the major axis and the line of 

 the solar motion lie in the same vertical plane, the result of his cal- 

 culations being that Saturn's motion in space is always in the same 

 direction as the sun's. 



Section III. contains the geometrical interpretation of the result 

 obtained in the preceding section, from which it appears that the 

 four exterior planets trace out progressive spirals in space. 



In Section IV. the author arrives at the conclusion that if an 

 encounter with meteors has occurred, Saturn, of all the planets, 

 would be most likely to accumulate them as a ring system. 



Section VI. contains the investigation of the circumstances of the 

 attachment of the meteors to the Saturnian system, from which 

 Lieut. Davies finds that, at a point 59,000 miles from the centre of 

 Saturn, the velocity of the meteors is about 61,592*4 miles per hour. 

 " Hence," he says, " if we subtract from this their velocity in com- 

 mon with Saturn in a direction at right angles to their motion at 

 this point, we shall have 33,3 78 '6 6 miles per hour for the velocity 

 of the meteors at that point in their orbit round Saturn, their cal- 

 culated velocity being 33,7 14*3 miles per hour. This is, I think, 

 conclusive as to the meteoric origin of the rings." 



