180 A MODEL OF NATURE. 



unlike a material inediuin, in that it is nonviscous; and that the 

 particles, if they exist, are so constitued that energy is not frittered 

 away when they collide. In either case we are dealing with some- 

 thing different from matter itself in the sense that, though it is the 

 basis of matter, it is not identical in all its properties with matter. 



The idea therefore that entities exist possessing properties different 

 from those of matter in bulk is not introduced at the end of a long 

 and recondite investigation to explain facts with which none but 

 experts are acquainted. It is forced upon us at the very threshold of 

 our study of nature. Either the properties of matter in bulk can not 

 be referred to any simpler structure, or that simpler structure must 

 have properties different from those of matter in bulk as we directly 

 knew it — properties which can only be inferred from the results which 

 they produce. 



No a priori argument against the possibility of our discovering the 

 existence of quasi-material substances, which are nevertheless different 

 from matter, can prove the negative proposition that such substances 

 can not exist. It is not a self-evident truth that no substance other 

 than ordinary matter can have an existence as real as that of matter 

 itself. It is not axiomatic that matter can not be composed of parts 

 whose properties are different from those of the whole. To assei't 

 that even if such substances and such parts exist no evidence, however 

 cogent, could convince us of their existence is to beg the whole ques- 

 tion at issue ; to decide the cause before it has been heard. 



We must therefore adhere to the standpoint adopted by most scien- 

 tific men, viz, that the question of the existence of ultraphysical enti- 

 ties, such as atoms and the ether, is to be settled by the evidence, and 

 must not be ruled out as inadmissible on a priori grounds. 



On the other hand, it is impossible to deny that, if the mere entry 

 on the search for the concealed causes of physical phenomena is not a 

 trespass on ground we have no right to explore, it is at all events the 

 beginning of a dangerous journey. 



The wraiths of phlogiston, caloric, luminiferous corpuscles and a 

 crowd of other phantoms haunt the investigator, and as the grim host 

 vanishes into nothingness he can not but wonder if his own concep- 

 tions of atoms and of the ether 



shall dissolve, 



And, like this insubstantial pageant faded. 



Leave not a wrack behind. 



But though science, like Bunyan's hero, has sometimes had to pass 

 through the "Valley of Humiliation," the specters which meet it there 

 are not really dangerous if they are holdl}' faced. The facts that mis- 

 takes have been made, that theories have been propounded, and for a 

 time accepted, which later investigations have disproved, do not 



