884: 



THE KEGOLITH 



break through the thin crust and sink to their shoulders in these 

 holes. ' ' 



J. B, Hatcher states^ that along the valleys and bluffs of the 

 smaller rivers of Patagonia rodents are extremely abundant and 

 often the entire earth for a depth of nearly two feet is literally 

 undermined over areas of many square miles with subterranean 

 passages which greatly impede the traveler, whose horse drops 

 in at every step, half way to the knee. 



The action of plant life in the accumulation of vegetable 

 mould has been fully discussed under the head of cumulose 



and alluvial deposits. 

 There is, however, one 

 phase of action which may 

 well be mentioned here. A 

 growing tree sends its roots 

 deep down into the earth in 

 '>Ssf^U'^" ^ores*^o^^<^ search of food and foot- 



hold- So long as the tree 

 remains alive and standing, 

 in firm soil the amount of 

 change in the soil itself, 

 except in the way of ab- 

 FiG. 41. straction of certain constit- 



uents taken up by the 

 growing plant, is presum- 

 ably very small. When, 

 however, the tree dies, 

 'porestMouu thc roots slowly decay, 

 ^«« ^""'^ and besides yielding up 



'"^ ^ ^ new soil, afford passage- 



-pij^ 40 ways for percolating 



* • water with all its atten- 



dant results. Moreover, cases are by no means rare in which 

 trees are upturned by the winds, bringing entangled in their 

 roots it may be tons of soil and boulders which in part gradually 

 fall back into the hole and in part remain to form a mound which 

 marks the spot long after the tree has decayed. Into the cavity 

 formed, dead leaves and other organic debris accumulate, which 

 in time form deep rich loam to be commingled with the stony 



^National Geographic Magazine, Ko. 11, 1897, p. 318. 



B&d Mock. 



