22 Mr. J. Croll on What determines Molecular Motion ? — 



physical energies ? What is it that directs the operation of those 

 energies. 



But in ascertaining whether chemistry and physics can explain 

 the mystery of nature, the point we have to eo&sider is whether 

 or not there is any thing in the known modes of operation of 

 physical and chemical energies which can in any way account 

 for the determination of molecular motion. If the advocates of 

 the physical theory can show that the modes of operation of those 

 energies do explain the determinations of molecular movement^ 

 then their theory is established, and the ulterior question as to 

 what is the cause of those modes of operation will be worthy 

 of consideration, for it will then in reality be the grand pro- 

 blem of nature. But if the modes of operation of physical and 

 chemical agencies do not account for the determination of mole- 

 cular motion, the physical theory must be abandoned, and the 

 solution of the mystery of life and nature must be sought for 

 somewhere else than in chemistry and physics. 



Enormous advance has been made in molecular physics and 

 in the science of energy of late years. But it has not thrown 

 much additional light on the cause of the determination of 

 molecular motion^ the reason being that the discoveries relate 

 more to the quantitative relationships of energy than to the 

 modes of its operation. It has been found that the total 

 quantity of energy remains constant, that whatever disappears 

 under one form reappears under some other form, and that, 

 whatever may be its form, its amount can be determined in ab- 

 solute measure. Take for example Heat, the form of energy in 

 regard to which the greatest advance has been made. Heat has 

 been demonstrated to be a mode of motion; and the amount of 

 energy represented by a given mass of any substance raised by 

 a given number of degrees in temperature can be determined in 

 mechanical units. 



We know heat to be some mode of molecular motion ; but we 

 do not as yet know with certainty what that mode is. JMost 

 physicists suppose it to consist of a sort of vibratoiy or oscilla- 

 tory motion of the molecules, while others conceive it to consist 

 of some sort of molecular vortices. But although the mode of 

 motion has not been determined, nevertheless the velocity of the 

 moving molecules can be estimated. This, however, does not 

 enable us in any way to explain how heat can determine mole- 

 cular motion in organic nature. If we knew the nature of that 

 mode of motion which constitutes heat, it might possibly be of 

 some service ; but a knowledge of the quantity of motion can 

 throw no light on the matter. Heat no doubt is an essential 

 condition to the formation and growth of all living things, whether 

 plants or animals ; but heat is evidently not the determining cause 



