402 FRAGMENTS OF SCIENCE. 



oration continues, solidifi cation goes on, and we finally 

 obtain through the clustering together of innumerable 

 molecules, 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 traveler in 

 Egypt is dragged by his guides. The human mind is as 

 little disposed to look without questioning at these pyra- 

 midal salt-crystals, as to look at the pyramids of Egypt, 

 without inquiring 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 the molecules act upon each other 

 without the intervention of slave labor; that they attract 

 each other, and repel each other, at certain definite points, 

 or poles, and in certain definite directions; and that the 

 pyramidal form is the result of this play of attraction and 

 repulsion. While, then, the blocks of Egypt were laid 

 down by a power external to themselves, these molecular 

 blocks of salt are self-posited, being fixed in their places by 

 the inherent forces with which they act upon each other. 



I take common salt as an illustration, because it is so 

 familiar to us all; but any other crystalline substance would 

 answer my purpose equally well. Everywhere, in fact, 

 throughout inorganic nature, we have this formative power, 

 as Fichte would call it this structural energy ready to 

 come into play, and build the ultimate particles of matter 

 into definite shapes. The ice of our winters, and of our 

 polar regions, is its handiwork, and so also are the quartz, 

 feldspar, and mica of our rocks. Our chalk-beds are for the 

 most part composed of minute shells, which are also the 

 product of structural energy; but behind the shell, as a 

 whole, lies a more remote and subtle formative act. These 

 shells are built up of little crystals of calc-spar, and, to 

 form these crystals, the structural force had to deal with 

 the intangible molecules of carbonate of lime. This ten- 

 dency on the part of matter to organize itself, to grow into 



