POLAR ICE-CAPS AND SEA LEVELS. 345 



weight to it, and it will yield. So a bar of cold ice 

 several degrees below freezing point in an atmo- 

 sphere at least 8 or 10 degrees below freezing point 

 was found to elongate by one third per cent, per 

 24 hours ; and the stress was 2 kilos, per square 

 centimetre. So also look at the shoemaker's wax 

 filling this model, which illustrates the principal 

 features in the path of say a Swiss glacier : not 

 warm, but cold as it is here now, it will keep yield- 

 ing constantly from year to year ; working its way 

 down this precipice, through this gorge, down this 

 next precipice, out through this hole, and ultimately 

 falling over the edges. Although it is brittle, it goes 

 on day after day, month after month, yielding. I 

 am not aware if my audience knows, what every- 

 body knew many years ago, that a sealed letter left 

 a long time seal down, flattens the seal with its own 

 weight. We were always warned in those days not 

 to seal letters for the tropics. Thus if you give it 

 time enough, you will find the wax (alluding to the 

 former model glacier) yielding, yielding, and yield- 

 ing, according to the same laws, precisely as this 

 mass of wax has yielded, aided by heat, in ten 



