72 FRAGMENTS OF SCIENCE 



and in strict accordance with this hexangular type, every 

 ice moleciile takes its place upon our ponds and lakes 

 during the frosts of winter. To use the language of an 

 American poet, "the atoms march in tune," moving to 

 the music of law, which thus renders the commonest 

 substance in nature a miracle of beauty. 



It is the function of science, not, as some think, to 

 divest this universe of its wonder and mystery, but, as 

 in the case before us, to point out the wonder and the 

 mystery of common things. Those fern-like forms, which 

 on a frosty morning overspread your window-panes, illus- 

 trate the action of the same force. Breathe upon such a 

 pane before the fires are lighted, and reduce the solid 

 crystalline film to the liquid condition; then watch its 

 subsequent resolidification. You will see it all the better 

 if you look at it through a common magnifying glass. 

 After you have ceased breathing, the film, abandoned 

 to the action of its own forces, appears for a moment 

 to be alive. Lines of motion run through it; molecule 

 closes with molecule, until finally the whole film passes 

 from the state of liquidity, through this state of motion, 

 to its final crystalline repose. 



I can show you something similar. Over a piece of 

 perfectly clean glass I pour a little water in which cer- 

 tain crystals have been dissolved. A film of the solu- 

 tion clings to the glass. By means of a microscope and a 

 lamp, an image of the plate of glass is thrown upon the 

 screen. The beam of the lamp, besides illuminating the 

 glass, ^Iso heats it; evaporation sets in, and at a certain 

 moment, when the solution has become supersaturated, 

 splendid branches of crystal shoot out over the screen. 

 A dozen square f^et of surface are now covered by those 



