228 FRAGMENTS OF SCIENCE' 



given, not the' art of the refiner, but the instinct of the 

 discoverer, and the strength of the delver who brings ore 

 from the recesses of the mine. That ore may contain its 

 share of dross, but it also contains the precious metal 

 which gives employment to the refiner, and without which 

 his occupation would depart. 



Let us dwell for a moment upon this subject of ancient 

 glaciers. Under a flask containing water, in which a ther- 

 mometer is immersed, is placed a Bunsen's lamp. The wa- 

 ter is heated, reaches a temperature of 212°, and then begins 

 to boil. The rise of the thermometer then ceases, although 

 heat continues to be poured by the lamp into the water. 

 "What becomes of that heat? We know that it is con- 

 sumed in the molecular work of vaporization. In the ex- 

 periment here arranged, the steam passes from the flask 

 through a tube into a second vessel kept at a low tem- 

 perature. Here it is condensed, and indeed congealed to 

 ice, the second vessel being plunged in a mixture cold 

 enough to freeze the water. As a result of the process 

 we obtain a mass of ice. That ice has an origin very 

 antithetical to its own character. Though cold, it is the 

 child of heat. If we removed the lamp, there would be 

 no steam, and if there were no steam there would be no 

 ice. The mere cold of the mixture surrounding the sec- 

 ond vessel would not produce ice. The cold must have 

 the proper material to work upon; and this material — 

 aqueous vapor — is, as we here see, the direct product 

 of heat. 



It is now, I suppose, fifteen or sixteen years since I 

 found myself conversing with an illustrious j)hilosopher 

 regarding that glacial epoch which the researches of Agas- 

 siz and others have revealed. This profoundly thoughtful 



