7 o6 THE POPULAR SCIENCE MONTHLY. 



ence limits so narrow that all attempts to bring the characteristic 

 phenomena of organic life (not to speak of mental action) within them 

 are utterly hopeless. Nevertheless, it is asserted that organic phe- 

 nomena are the product of ordinary physical forces alone, and that 

 the assumption of vital agencies, as distinct from the forces of inor- 

 ganic Nature, is wholly inadmissible. In view of this, it seems strange 

 that the validity of the proposition above referred to has never, so far 

 as I know, been questioned, except in the interest of some metaphysi- 

 cal or theological system. It is my purpose in the following essays 

 to offer a few suggestions in this behalf, in order to ascertain, if pos- 

 sible, whether the prevailing primary notions of physical science can 

 stand, or are in need of revision. 



One of the prime postulates of the mechanical theory is the atomic 

 constitution of matter. A discussion of this theory, therefore, at 

 once leads to an examination of the grounds upon which the assump- 

 tion of atoms, as the ultimate constituents of the physical world, 

 rests. 



The doctrine that an exhaustive analysis of a material body into 

 its real elements, if it could be practically effected, would yield an ag- 

 gregate of indivisible and indestructible particles, is almost coeval 

 with human speculation, and has held its ground more persistently 

 than any other tenet of science or philosophy. It is true that the 

 atomic theory, since its first promulgation by the early Greek philoso- 

 phers, and its elaborate statement by Lucretius, has been modified and 

 refined. There is probably no one, at this day, who invests the atoms 

 with hooks and loops, or (Lucretius, De Merurn JVatura, ii., 398, et seq.) 

 accounts for the bitter taste of wormwood by the raggedness, and for 

 the sweetness of honey by the smooth roundness of the constituent 

 atoms. But the " atom " of modern science is still of determinate 

 weight, if not of determinate figure, and stands for something more 

 than an abstract unit, even in the view of those who, like Boscovich, 

 Faraday, Ampere, or Fechner, profess to regard it as a mere centre of 

 force. And there is no difficulty in stating the atomic doctrine in 

 terms applicable alike to all the acceptations in which it is now held by 

 scientific men. Whatever diversity of opinion may prevail as to the 

 form, size, etc., of the atoms, all who advance the atomic hypothesis, 

 in any of its varieties, as a physical theory, agree in three propositions, 

 which may be stated as follows : 



1. Atoms are absolutely simple, unchangeable, indestructible / they 

 are physically, if not mathematically, indivisible. 



2. Matter consists of discrete parts, the constituent atoms being 

 separated by void interstitial spaces. Hi contrast to the continuity of 

 space stands the discontinuity of matter. The expansion of a body 

 is simply an increase, its contraction a lessening of tJie spatial inter- 

 vals between the atoms. 



3. TJie atoms composing the different chemical elements are of de- 



