194 NATURE-STUDY REVIEW [15:5— May, 1919 



what he needed. She has been a wonderful home-maker, appar- 

 ently forgetting nothing needful to the human race. Soil was 

 essential to life, so the earth's machinery was set in motion to 

 produce soil. In the beginning — or originally, if you prefer the 

 expression for carrying you back in imagination to the time when 

 this world of ours was barren rock — there were no growing things 

 of any kind, no form of life as we know it. There was not even 

 water upon the earth; the planet was bone-dry. When the 

 chemical condition of the rock became such as to attract moisture 

 from the atmosphere in sufficient quantities, oceans were formed. 

 And for some reason known only to Nature the first ocean-water 

 was fresh. Then after a time plant-life first made its appearance 

 around the water's edge. It was at this period, approximately, 

 that Nature, who has a way of looking into the future, realized the 

 necessity of producing soil. So she set her machinery to work and 

 kept it steadily running night and day for ages before the soil was 

 ready to support the many kinds of life that were to feed upon it. 

 Even then the work did not stop ; indeed the same machinery is 

 in motion today, turning out its incessant crop of soil. 



There is no labor problem in Nature's shops — no strikes, no 

 stopping for repairs. The earth's soil-producing machinery is 

 made of many parts. These parts neither break nor wear out. 

 Each has a special purpose; there is complete co-operation, and 

 under the direction of the Supreme Mechanician — Nature — the 

 machinery is unceasingly in motion. 



Perhaps the most important part of this soil-making machinery 

 was the glacier. A glacier may well be called Nature's ice-mill; 

 that is really what it is. Once upon a time, back in the early days 

 of the planet, there was a drop in the temperature and the water on 

 the surface of the earth froze and took on the form of glaciers. 

 These great rivers of ice have been breaking, grinding and pulveriz- 

 ing the rock and getting it in shape for the elements to finish the 

 work of transforming it into soil. 



The glacier slowly plows through mountains of rock, leaving 

 smooth-walled canyons in its wake, and carries with it enormous 

 masses of the rock-surface crushed and ground to dust. Some- 

 times the process is on a still larger scale, when whole mountains 

 are reduced to the level of valleys and plains. Most of the soil 

 now covering the states of Illinois, Indiana, Ohio, Iowa and North 

 Dakota is the product of the glacier. In fact all the Northern part 



