NITROGEN RETENTION 609 



night and who said: " There many a puzzle must yield its 

 secret, " with the reply: "Yet many a puzzle, too, is twin- 

 ing its tangle there." Here in fact, as so often in our 

 wandering, we find ourselves hemmed in at each step of the 

 way by a world of new enigmas for which the future alone 

 will find a solution. At all events, however, we must ac- 

 knowledge our indebtedness to all those men to whom the 

 thirst for knowledge lent power and energy to endure up 

 there upon icy mountain-heights, with the roar of storms 

 about them, for many weeks at a stretch, cold, loss of sleep, 

 bodily discomforts and privations of every sort, and to 

 carry on from day to day with fixed purpose and with pa- 

 tience their arduous and often tedious work of investigation. 



