372 PRACTICAL LESSONS IN SCIENCE. 



two portions now differ in level. There are upward and down- 

 ward movements in Norway and Sweden and along the Mediter- 

 ranean sea. There are volcanoes and occasional earthquakes, 

 showing that one group of geological forces is still in operation. 

 The formation of sediments along river beds and at their 

 mouths, along the shores of lakes and of the sea, the formation 

 of sand dunes, of bog iron ore, and bog limestone, and the action 

 of rain and frost, etc., in furnishing the materials for the sedi- 

 ments, shows another set of forces at work also. The geological 

 agencies are doubtless working just as vigorously at the present 

 as ever in the history of the earth; but one set works so slowly 

 that we do not notice them, and the others are so common that 

 we do not think of them as geological. 



The large and fierce animals that dominated the Quaternary 

 age passed away, and those of a smaller size and more tractable 

 disposition appeared in their stead. And the earth, with pure 

 air and water, with temperate climate, with useful plants and 

 animals, after ages of preparation at last became a fit place for 

 the home of man. 



Man has doubtless lived on the earth for many centuries, was 

 contemporary with many of the large mammals, and with the 

 later events of the Glacial and Champlain periods, but does not 

 seem to have become the dominant type of life until quite recent 

 times. Remains of man are found in caverns, lake beds, peat 

 bogs and similar places, and we find the tools of bone, wood 

 and stone which he used ; and we may know something of how 

 he lived from finding fragments of bones and shells with tools, 

 etc., in caves, and at particular places along the shores of lakes 

 and seas. But the story told by these remains is very fragmen- 

 tary and not easily interpreted, but seems to indicate at least a 

 low stage of culture for primitive man. 



Considered as an animal, man's appearance on the earth was 

 abrupt, as abrupt as the appearance of vertebrates in the Dev- 

 onian, and this idea is intensified when we consider man's intelli- 

 gence. 



What is th ag of the earth? This is an interesting question, 



