REVIEWS 693 



the transformation of radioactive elements contained in various minerals which 

 gives rise to a continual evolution of helium. The first two methods yield results 

 which agree very well with a period of the order of 100 millions of years, the 

 balance of probability being that this is somewhat too great. The measurements 

 based on the evolution of radioactive products yield results which in their superior 

 limits exceed those derived above from nine to fourteen times. However, 

 Dr. Joly points out the weakness of certain assumptions employed in the third 

 method of investigation, and shows that we have grave reason to question the 

 existence throughout the ages of a uniform rate of evolution of radioactive 

 products. 



In an essay on the " Abundance of Life," the author inquires into the under- 

 lying causes of the advance of life upon the earth, the " aggressiveness of vitality " 

 — to use his picturesque phrase. He finds them to be, physically, more funda- 

 mental than evolution, and to be dynamical rather than naturally selective. In 

 the general dynamic conditions attending the motions of inanimate matter, we 

 find ever present that dissipation of available energy — at one time mainly gravita- 

 tional potential energy — into heat, whose course is summarised in the Second Law 

 of Thermodynamics. In the general dynamic conditions attending the behaviour 

 of animate bodies, such as the absorption of energy by a leaf, the division of the 

 leaf so as to open up new channels of supply, the flattening of its form, the 

 orientation of its greatest surface towards the source of energy, we find an 

 f. attitude " towards available energy which causes an accelerated transfer and 

 retards dissipation. It is this active attitude, rather than the passive one implied 

 in natural selection, which determines progress. 



A paper entitled " Other Minds than Ours" discusses the possibility that the 

 well-known markings on the surface of Mars — usually called the " Martian 

 Canals"— may indicate the existence of intelligent beings in that planet. Prof. 

 Lowell, who has just died, extended the early observations of Schiaparelli, and 

 has been a most uncompromising advocate of the view that Schiaparelli's 

 " canali " — mistranslated " canals " — were the work of a highly advanced civilisa- 

 tion seeking to store its fast-dwindling water supplies by draining the water 

 obtained from melting polar snows into huge oases, and transmitting it to its 

 populous centres, presumably studded along the banks of these huge artificial 

 rivers and living on the rich alluvial plains created by such an immense irrigatory 

 system. Dr. Joly, while not combating this view, points out that in so far as it 

 has been accepted, the acceptance is due to the exclusion of other less probable 

 alternatives rather than to any strong positive evidence in its favour, and he puts 

 forward a new hypothesis which certainly cannot be put aside as an unlikely 

 alternative to Lowell's belief. He remarks that many of the small asteroidal 

 bodies which populate that part of the solar system lying between the planets 

 Mars and Jupiter cut across the orbit of Mars at certain times. It is not im- 

 probable that some of them are thus drawn towards Mars and become satellites 

 of it — in fact this is probably the history of Phobos and Deimos. Some of these 

 especially if their orbital motion round Mars happened to be opposite to the 

 planet's axial rotation, would be gradually drawn in and finally crash down on the 

 surface. Before doing so, however, such a satellite would travel many times 

 round the planet at such a close distance that its gravitational attraction would 

 probably rend the crust along two lines parallel to the projection of its path on the 

 surface and lying to right and left of it. This would account for the well-known 

 double character of these surface markings. Their form and curvature would 

 depend on the velocity of the satellite and the axial rotation of Mars, and it 



