80 FRAGMENTS OF SCIENCE. 



stones, and, guided by the volition, the skill, and 

 possibly at times by the whip of the architect, placing 

 them in their proper positions. The blocks, in this 

 case, were moved and posited by a power external to 

 themselves, and the final form of the pyramid expressed 

 the thought of its human builder. 



Let us pass from this illustration of constructive 

 power to another of a different kind. When a solution 

 of common salt is slowly evaporated, the water which 

 holds the salt in solution disappears, but the salt itself 

 remains behind. At a certain stage of concentration 

 the salt can no longer retain the liquid form ; its 

 particles, or molecules, as they are called, begin to 

 deposit themselves as minute solids so minute, indeed, 

 as to defy all microscopic power. As evaporation con- 

 tinues, solidification goes on, and we finally obtain, 

 through the clustering together of innumerable mole- 

 cules, a finite crystalline mass of a definite form. 

 What is this form ? It sometimes seems a mimicry 

 of the architecture of Egypt. We have little pyramids 

 built by the salt, terrace above terrace from base to 

 apex, forming a series of steps resembling those up 

 which the traveller in Egypt is dragged by his guides. 

 The human mind is as little disposed to look without 

 questioning at these pyramidal salt-crystals, as to look 

 at the pyramids of Egypt, without enquiring whence 

 they came. How, then, are those salt-pyramids built 

 up? 



Guided by analogy, you may, if you like, suppose 

 that, swarming among the constituent molecules of the 

 salt, there is an invisible population, controlled and 

 coerced by some invisible master, placing the atomic 

 blocks in their positions. This, however, is not the 

 scientific idea, nor do I think your good sense will 

 accept it as a likely one. The scientific idea is, that 



