i 9 4 



ALASKA GLACIERS 



or spit was completed, another was built outside it, and so 

 on to the number of six or more. The one next the sea 

 has a crest considerably above high-tide, at the extreme 

 limit reached by storm waves, and the top of it is covered 

 by drift-wood, to which annual additions are doubtless 

 made. The next bar, lying back of this and parallel to 

 it, is six feet lower. It also is covered by drift-wood, but 

 the wood is decayed, so that no sound logs were found. 

 Two others are successively lower and have no drift- 

 wood, and the innermost are so low as to be covered by 

 the water of the bay. It is evident that each of these 

 ridges of shingle was formed by storm waves at the shore, 

 and we may assume that its crest height was originally as 

 far above high-tide as the crest of the outer ridge is now. 

 The existing differences in height have resulted from the 

 gradual sinking of the land, and a rude indication of the 

 rate of sinking is given by the drift-wood. The inner 

 ridges were made so long ago that the drift-wood they 

 originally bore has rotted away and disappeared. The 

 age of the second ridge has given time for only the partial 

 decay of the timber upon it, and the inference is that the 

 island has sunk to the extent of six feet in a period less than 

 that necessary for the complete destruction of logs through 

 the processes of decay. 



