102 SCIENCE PROGRESS 



in the Sun. Dr. Johnstone is discussing the restoration of 

 energy, not on the Earth, but in the Universe ; and we can no 

 more decide the attributes of the Universe by the capacities of 

 Liverpool than we can decide the attributes of God by the 

 capacities of the Lord Mayor. 



Hydriodic gas is another endothermic compound which is 

 formed by itself at ordinary temperatures when sulphuretted 

 hydrogen passes through iodine suspended in water : there are 

 many other endothermic substances, as, for instance, hydrazoic 

 acid ; and of all these it can be said that they occur by themselves. 

 In physics, as well as in chemistry, absorption of dissipated 

 heat happens too constantly to require mention. It happens 

 when a gas expands against external pressure ; when water 

 evaporates ; when crystals are dissolved in water ; when snow 

 is mixed with salt, etc. In some cases the dissipated energy of 

 heat is concentrated into a new form of much higher potential 

 than any previously present. A slight rise of temperature 

 over the ocean causes many tons of water to rise into the sky, 

 where they become condensed as clouds. These are precipitated 

 as rain which gives rise to a kinetic energy that may easily be 

 reconverted into heat of a far higher potential than existed at 

 the commencement of the operations. 



Dr. Johnstone appears in short to have misapplied the 

 second law of thermodynamics. When a gas expands against 

 external pressure, it becomes cooled below the temperature of 

 surrounding objects ; but that is no breach of the law, for if 

 the gas were restored to its original condition, the cycle of 

 operations would display some dissipation of heat. The heat 

 evolved in the second part of the process would be greater than 

 the heat absorbed in the first part. Similarly in the case of 

 plants the synthesis of compounds of high energy value involves 

 some absorption of heat ; but this again does not contradict the 

 law, for if the compounds were broken up again into their former 

 constituents, the certain result of the entire operation would in- 

 volve a certain dissipation of heat. Dr. Johnstone fails absolutely 

 therefore to show the slightest deviation on the part of organisms 

 from the second law of thermodynamics ; he fails to name a 

 single condition in the synthesis of organic compounds which 

 is not realised in " free " nature, far from the dwellings of any 

 human experimentalist. Certain secondary considerations are 

 "raised by Dr. Johnstone in the course of his article; but I 



