572 THE IGE AGE W NORTH AMERICA. 



nology of the Glacial age by studying the smaller kettle-holes 

 which constitute so marked a feature in the kames and 

 moraines of the glaciated region. As already shown, the most 

 satisfactory explanation of these curious depressions is, that 

 they mark places where masses of ice were buried in the 

 debris of sand and gravel brought down by the streams of 

 the decaying glacier ; and where, upon the melting of the 

 buried ice, a cone-shaped depression was left with sides as 

 steeply inclined as the nature of the soil would permit. At 

 any rate, there can be no question that the kettle-holes were 

 formed during the closing stages of the Glacial period. 



As typical of numberless others we present the facts 

 concerning a kettle-hole near Pomp's Pond in Andover, 



Pomp's Pond is itself a moraine basin about a quarter of a 

 mile in diameter, and but slightly above the level of the Shaw- 

 shin River, into which it empties. Upon its north side is an 

 accumulation of gravel and sand, with pebbles intermingled, 

 in which there are several of the smaller characteristic bowl- 

 shaped depressions of which we have spoken. Their appear- 

 ance is much like that of volcanic craters. You ascend a 

 sharp acclivity from every side to a rim of gravel, and then 

 descend as rapidly into the bowl-shaped or crater-like depres- 

 sion. A section carried across will present the idea. 



Fig. 147.— Section of kettle-hole near Pomp's Pond. Andover, Massachusetts. (See text.) 

 (For general view of the situation, see Fig. 101, p. 338). 



From the level of the pond, and two or three rods from the 

 edge, you begin to ascend at an average rate of about one foot 

 in three, till the south side of the rim is reached, at a height 

 of fifty -two and five tenths feet above the pond, (a) (This rim 

 is not, however, of a uniform height. On the east side it rises 



* I here transfer a few paragraphs from my " Studies in Science and Re- 

 ligion.*' 



