380 Notices of Books. [July, 



optic nerve. But suppose the water withdrawn, the action at a 

 distance would then cease, and as far as the sense of touch is 

 concerned, the wader would be first rendered conscious of the 

 motion of the wheel by the actual blow of the paddles. The 

 transference of motion from the paddles to the water is 

 mechanically similar to the transference of molecular motion 

 from the heated body to the aether; and the propagation of 

 waves through the liquid is mechanically similar to the propa- 

 gation of light and radiant heat." 



But the power of this work most certainly culminates in the 

 essay on the Scientific Use of the Imagination. Such an article 

 is a true index of the liberality of present scientific investigation, 

 and a true growth of the grand scheme of inductive logic. No 

 reader of this essay can predict a limit to experimental philosophy, 

 can say how soon electricity and magnetism may have supplied 

 by a thoughtive imagination the missing links in the chain that 

 will some day assuredly show their connection with the wave- 

 theory of Light and Heat, binding the phenomena of nature in 

 a comprehensive whole. And when it is seen what imagination 

 has done for science, we cannot wonder that the pioneers of 

 science acquire fresh energy to strike out new paths in the 

 wilderness of fact. What the compass is to the explorer, 

 Imagination is to the scientific investigator; both direct, but 

 neither limit the distance, to be found only by successive trials. 

 Most noticeable of all is the poetic feeling which the author 

 brings to bear upon his subject. There is an emotional under- 

 current that imperceptibly draws the student on to the more 

 fatiguing paths of inquiry: a vividness of mental vision well 

 illustrated, where it says, " The mind is, as it were, a photographic 

 plate, which is gradually cleansed by the effort to think rightly, 

 and which when so cleansed, and not before, receives impressions 

 from the light of truth." 



The Meteoric Theory of Saturn's Rings. By Augustus Morse 

 Davies, B.A., F.R.A.S., &c. London: Longmans, Green, 

 and Co. 



This consideration of the Meteoric Theory results from seed 

 sown by Mr. Proctor's " Saturn and its System," which induced 

 the endeavour to think out the question of the accumulation of 

 such an assemblage of minute attendants on this one member 

 of the solar system. The work deals shortly and decisively 

 with those elements of Saturn distinguishing it from the other 

 planets, showing that, Jupiter excepted, Saturn from its extremely 

 low velocity is most favourably circumstanced for attaching 

 meteors in its train as satellites, particularly when the velocities 

 of the meteors are considered. Then the distance of Saturn 

 from the Sun exceeding that of Jupiter, Saturn's influence on 

 passing meteors would be greater than that exerted by Jupiter, 



