ESSAY-REVIEWS 101 



Except indeed in the ease of living organisms ! And I now 

 turn to this, the second part of Dr. Johnstone's argument. He 

 has established that there must be somewhere a restoration of 

 available energy : he has established it, that is, to his own 

 satisfaction, but not (I hope) to the satisfaction of readers of 

 Science Progress. He goes on to affirm that living organisms 

 effect that restoration. Plants absorb radiant energy for the 

 purposes of chemical synthesis. They exhibit therefore 

 endothermic reactions : that is to say, their chemical processes 

 are accompanied not by the evolution but by the absorption of 

 heat. This apparently he regards as opposed to the second law 

 of thermodynamics. He admits, of course, that endothermic 

 reactions do occur in inorganic substances ; but he says " they 

 do not occur of themselves." What does he mean by that? 

 Presumably that they only occur in human experiments. But 

 an experiment is simply a method of bringing together conditions 

 not very frequently or conveniently realised in nature. The 

 reaction occurs " by itself" ; and the peculiar set of conditions 

 under which it occurs may quite possibly and in course of time 

 must certainly happen to come together in nature, as we bring 

 them together in the laboratory. The entire activities of human 

 beings consist in altering the relative positions of objects, i.e. in 

 moving things. The whole work of man and power of man is 

 limited to moving objects from one place to another : and the 

 rest happens " by itself." An experiment is nothing more than 

 a rearrangement or transference of various objects ; and then the 

 same thing happens as would happen if the same collocation of 

 objects occurred in nature. If sulphur vapour passes over red- 

 hot carbon, carbon disulphide is formed. This is an endothermic 

 reaction, and it occurs " by itself." Presumably Dr. Johnstone 

 will answer that, except in a laboratory, you do not get sulphur 

 vapour in contact with red-hot carbon. You have to heat the 

 carbon, and then pass sulphur vapour over it. But surely, 

 although this particular reaction may not occur in the districts 

 frequented by Dr. Johnstone, he would find it occurring if he 

 were to make a descent into a volcano : and it certainly occurred 

 at large in early periods of the earth's history, and does now 

 occur in all parts of the Sun. Similarly acetylene is formed 

 when carbon and hydrogen come in contact at high temperatures. 

 The reaction again, like that of the plant, is endothermic : and it 

 occurs " of itself"; not perhaps in Liverpool, but at all events 



