1 2 WlLDE, Points of Chemical Philosophy. 



Although many years have elapsed since the above 

 paragraphs were written, I have found no sufficient 

 reason lo change the opinions expressed therein, but, on 

 the contrary, much to confirm the conviction that the 

 ultimate constitution of all substances, including the 

 universal medium (ether) that fills infinite space, is abso- 

 lutely inscrutable to human understanding. Not the 

 least valuable result of the study of mental philosophy is 

 the conscious realization of its limitations. Mathematical 

 science has no monopoly in the production of mental 

 wreckage, through the vain endeavours of some indi- 

 viduals to measure the incommensurables in geometry 

 and in numbers, and similar dangers beset the path of 

 unwary investigators of the, as yet, obscure phenomena of 

 radio-activity and atomic subdivision. A distinguished 

 cultivator of natural knowledge, Sir W. R. Grove, in his 

 epoch-marking book on the " Correlation of Physical 

 Forces,"* has expressed himself in similar terms with 

 reference to the limitations of man's knowledge of the 

 ultimate structure of " matter," and " the harm done by 

 attempting hypothetically to dissect it, and to discuss 

 the shapes, sizes, and numbers of atoms and their 

 atmospheres of heat and electricity." 



The doctrine that dynamic forces in molecular physics 

 are modes of motion mutually transformable, or, in other 

 words, qualities of substance and not specific entities, is 

 fully accepted by all who are versed in the history of 

 natural and mental philosophy. Nevertheless, some 

 eminent writers on radio-activity and sub-atomic me- 

 chanics fail to recognize the results of the labours of the 

 eminent philosophers who have established this doctrine 

 on a firm basis, as they revert to the corpuscular notions 

 prevalent in the seventeenth century, and discuss " atoms 

 *5th Edition, 1867. 



