15 



CHAPTER II. 



UNATTAINABLE OBJECTS OF SEARCH. 



There's nothing situate under Heaven's eye, 



But hath its bound in earth, in sea, or sky. SHAKSPEARE. 



IT is useless to search for that which cannot exist. 

 Although we know but little of the actual limits of pos- 

 sible knowledge, there are signs that nature is not in 

 every respect infinite. It is highly probable that the 

 number of forms of energy and of elementary substances 

 is limited. At the present time we are only acquainted 

 with less than a dozen of the former and six dozen of the 

 latter. Elementary substances also do not unite together 

 in every proportion by weight, but only in certain definite 

 ones, and do not produce an unlimited series of com- 

 pounds. There appear to be laws operating in the inmost 

 nature of elementary bodies, which prevent the atoms 

 uniting with each other, except in certain definite arrange- 

 ments or groups, as if all other arrangements were geo- 

 metrically or mechanically impossible. The number of 

 forms in which each substance crystallises is also very 

 limited ; common salt, for example, crystallises only in 

 cubes. But who, with a finite mind, shall set a limit to 

 creative power, or assign bounds to the Universe ? Ours 

 is the science of this globe alone, and consequently of its 

 limited conditions. Nearly all the instances of definite 

 chemical compounds with which we are acquainted are 

 observed under the limited ranges of pressure and tempe- 

 rature, &c., existing on this earth ; and it is possible and 

 even probable that under different ranges of pressure and 



