49 



fill study by a student of the subject of Griacial Geology will serve 

 to explain them. Each place lias had peculiar conditions and it 

 would be necessary to study each place carefully in order to explain 

 all the differences much further than has been done here. 



Not only is agriculture influenced greatly by the differences in 

 the soil from place to place, but also by the very fact that they are 

 glacial soils. In a soil that has been formed by the decay of rock 

 some of the materials needed by plants, the plant-foods, have been 

 leached out and carried off by the water while the rock was decay- 

 ing ; but the glacial soils have most of these foods still stored up for 



1 



27, — Hunwwcky moraine hills in the background and a level gravel plain — an 

 ancient glacial- stream flood- plain — in foreground. 



use. Here the minerals are simply ground up and not much 

 decayed, while in the other case they are badly decayed, the differ- 

 ence being something like that between iron filings which are able 

 to decay and rust and iron rust which is already decayed. 



Slowly the glacial soils are decaying, and, as they do so, are fur- 

 nishing plant-food to the water which the roots greedily draw in- 

 So the glacial soil is not a mere storehouse of plant food, but a 

 manufactory of it as well, and glacial soils are therefore " strong " 

 and last for a long time. That decay is going on, especially near 



the surface, may often be seen in a cut in this kind of soil, where 



441 



