308 The Realm of Nature CHAP. 



394. Life in the World. Geology and Oceanography 

 bear evidence of changes in structure which cannot be 

 explained by the laws of matter and energy. These laws 

 enable us to understand that water should in certain condi- 

 tions dissolve carbonate of lime and silica. But they cannot 

 account as yet for the opposite process which is at work in 

 exactly the same physical conditions. Carbonate of lime and 

 silica separate out from solution and assume the solid form, 

 not with the uniform sharp angles and smooth faces of crystals, 

 but with curved and varied outlines decorated with delicately- 

 etched designs of infinite variety ( 273). Fossils are evid- 

 ently due to a similar temporary reversal of ordinary chemical 

 and physical change. (These reversed processes are recog- 

 nised as the characteristic result of life. Geology may be said 

 to present us with a view of the world as a vast cemetery 

 full of monuments of past generations of living creatures. 

 When we look around us in the open country our eye is 

 not, as a rule, attracted by bare rocks or soil, but by a 

 covering of grass, flowers, and trees, amongst which beasts 

 and birds and insects are moving. These are the living 

 inhabitants of the great World House. Between them and 

 the rooms they inhabit there is a close and ever-varying 

 relation, the comprehension and description of which is the 

 central aim of Physiography. 



395. Classification of Living Creatures. Every one 

 can tell at a glance that a bush and a cow belong to widely 

 different classes ; indeed a close observer might fail to find 

 anything in common between them. It is easy and natural 

 to class trees, bushes, herbs, grass, and even seaweeds, as 

 essentially similar, and to recognise them all as Plants. 

 Similarly, although four-footed beasts, birds, reptiles, insects, 

 and fishes, differ a good deal amongst themselves, they are 



sed together, almost without a thought, as Animals. A 

 it gulf seems to separate the Vegetable and Animal 

 kingdoms, to use the names given by Linnaeus who laid the 

 foundations of the modern classification of creatures. Plants 

 are rooted in the soil ; animals are free to move over the 

 land, through the water or air. When carefully studied 

 both of the great kingdoms are found to fall into a number 



