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VIII. Notices respecting Neiv Books, 



Stellar Evolution and its Relations to Geological Time. By James 

 Croll, LL.D., F.B.S.. author of ' Climate and Time,' Sfc. 

 London : Stanford. 



TN this little volume Dr. Croll continues and expands bis now 

 *- classic researches into the relations of Time and Geological 

 Evolution. His investigations and speculations he now boldly 

 carries to the utmost boundaries of time — if time is finite, and to 

 the morning of creation, not only of the Earth and the solar 

 system, but of the entire stellar universe. Beyond the point to 

 which Dr. Croll ventures by his scientific imagination to pierce, 

 Science certainly is not entitled to travel ; but there is little doubt 

 that long ere opinion finally settles itself into fixed belief as to that 

 remote point and the cycle of events by which the starry hosts have 

 come to be what they now appear, there will be many speculations 

 to be hazarded, and many suggestions offered. Meantime we can 

 only say that Dr. Croll has made a brave plunge into the unex- 

 plored ; and if he has not finally settled the theory of creation, he 

 has at least made a most substantial contribution towards the dis- 

 cussion of the great problem in physics which yet remains for 

 philosophers of the foremost rank to settle. 



The germ of the theory expounded in 'Stellsr Evolution' ap- 

 peared in the pages of the Philosophical Magazine so long ago as 

 May 1868. It was further expanded in ' Climate and Time,' and 

 in the more recent work ' Climate and Cosmology.' Through an 

 inquiry into the possible origin and age of the sun's heat, Dr. Croll 

 is led to adopt and support the theory that the whole visible uni- 

 verse is the result of the collision of vast dark masses which have 

 travelled through limitless space at various velocities and in inde- 

 pendent paths. Thus with matter and motion in their most 

 elementary condition the phenomena of creation began ; and the 

 progressive series of changes which we call Evolution only came 

 into play when in boundless time and space two of these mighty 

 dark masses clashed together, and by the partial or complete 

 stoppage of their motion begat that energy of condition which 

 manifested itself by the expansion of the solid masses into a gaseous 

 nebula of enormous extent, heat, tenuity, and, from dissociation, 

 of uniform chemical character. A nebula so created possesses a 

 store of heat measured by the mass of the colliding bodies and 

 the rate at which they were travelling at the period of collision. 

 There is indeed no necessary limit to the store of energy which 

 might in this way be vested in a nebulous mass. Dealing with 

 gravitational energy alone, on the other hand, the amount available 

 in any system is strictly limited. It has been shown by Helmholtz 

 and Sir William Thomson that the solar system cannot be older 

 than from twelve to twenty millions of years if its heat is due to 

 gravitation alone. That amount of time Dr. Croll goes on to show 

 is utterly inadequate for the evolution of terrestrial phenomena, 

 and a considerable portion of his work is occupied in marshalling 



