KETTLE-HOLES 55 



that ice was approximately or wholly continuous, its melt- 

 ing, being temporarily concentrated here and there by 

 underground currents, would let the gravels down un- 

 equally and leave them, in the end, in a system of irregu- 

 lar heaps identical with kames. Where the surviving ice 

 comprised only isolated or scattered masses, the waste of 

 these would let down the gravels immediately above them, 

 producing steep-sided, crater-like kettle-holes, and creat- 

 ing the familiar phenomenon of a pitted plain. 



The upper figure in plate v reproduces a photograph of 

 one of these fresh-formed kettle-holes, lying near the visi- 

 ble portion of the glacier. Its dimensions were 220 feet 

 by 70 feet, with a depth, to the water surface, of eight feet. 

 Its wall was divided at one point by an outlet channel 

 leading to a neighboring glacial creek. An incipient 

 kettle-hole seen about a mile below the glacier is repre- 

 sented in the lower figure. This had been overflowed by 

 water from one of the glacial creeks, so as to receive a 

 layer of mud, but the water had retired before it was 

 wholly silted up. It is evident that the meandering of 

 streams over the gravel plain would eventually obliterate 

 all of the kettle-holes, so that their preservation must de- 

 pend upon some permanent diversion of the streams. 



The stream escaping from the north edge of the ice 

 front was traced backward to an ice cave among the hil- 

 locks constituting the lateral moraine. It was evident 

 from an examination of the local topography of the ice 

 surface that the debris had great influence on the rate and 

 method of wasting, and reciprocally, that the wasting 

 modified the distribution of the debris. Where the de- 

 bris was more than a few inches thick it retarded melting, 

 producing an ice hill; but from these hills the stones slid 

 down to the neighboring hollows, producing accumula- 

 tions which in turn retarded melting and caused a new 

 distribution of hills. Some of the hills were elongate, 



