70 FRAGMENTS OF SCIENCE 



And now we approach a new and wonderful display 

 of force. As long as the substance remains in a liquid 

 or vaporous condition, the play of this force is alto- 

 gether masked and hidden. But as the heat is gradually 

 withdrawn, the molecules prepare for new arrangements 

 and combinations. Solid crystals of water are at length 

 formed, to which we give the familiar name of ice. 

 Looking at these beautiful edifices and their internal 

 structure, the pondering mind has forced upon it the 

 question, How are they built up? We have obtained 

 clear conceptions of polar force; and we infer from our 

 broken magnet that polar force may be resident in the 

 molecules or smallest particles of matter, and that by 

 the play of this force structural arrangement is possible. 

 "What, in relation to our present question, is the natural 

 action of a mind furnished with this knowledge? It is 

 compelled to transcend experience, and endow the atoms 

 and molecules of which crystals are built with definite 

 poles whence issue attractions and repulsions. In virtue 

 of these forces some poles are drawn together, while 

 some retreat from each other; atom is added to atom, 

 and molecule to molecule, not boisterously or fortui- 

 tously, but silently and symmetrically, and in accord- 

 ance with laws more rigid than those which guide a 

 human builder when he places his materials together. 

 Imagine the bricks and stones of this town of Dundee 

 endowed with structural power. Imagine them attracting 

 and repelling, and arranging themselves into streets and 

 houses and Kinnaird Halls would not that be wonderful? 

 Hardly less wonderful is the play of force by which the 

 molecules of water build themselves into the sheets of ice 

 which every winter roof your ponds and lakes. 



