404 LIFE OF DALTOX : 



pause and further demonstration is lost in darkness. There 

 may be rashness indeed in marking too absolutely any line 

 of demarcation, for the science of our own day has often 

 swept over what seemed to be the final limits of our know- 

 ledge, and carried its adventure into open fields beyond. 

 The subject before us, moreover, is one where physical evi- 

 dences still crowd in from so many separate and unexpected 

 sources, that it is hard to curb the efforts of the mind to 

 theorise upon the results already obtained. 



This very multiplication of proofs is in itself a hindrance 

 to a concise and popular view of the modern atomic doctrine. 

 The physical evidence is not merely various in its sources, 

 but presents peculiar modifications, adding much to its com- 

 plexity. The recent discoveries in Isomorphism, Isomerism, 

 and Allotropy (names in themselves formidable to the ear), 

 indicating some of the various modes in which the. molecules 

 of matter, simple or compound, are related to or act upon 

 one another, all bear essentially on the question of the 

 atomical constitution of bodies ; and require an interpretation 

 accordant at least, if not common to all. An elementary 

 view of the subject is further embarrassed by the anomalous 

 or doubtful points which still remain for solution ; such as 

 the case of a numerical series, perfect in its other parts, being 

 stopped by an anomalous fraction, only to be removed by 

 such better analysis as may bring the refractory element into 

 the scale from which it seemingly departs, or by altering 

 the first term so as to convert the fraction into a simple 

 number in the series. 



The statement of these difficulties is not altogether without 

 its use. It suggests, first, the demarcation, as far as this can 

 be drawn, between the metaphysical and physical parts of 

 the atomic philosophy; between that which is purely or 

 chiefly speculative, and that which depends on experiment 

 and is expressed by formulae of numbers. And secondly, in 



