Hamilton. — On Formation of Quartz Pebbles of Southland Plains. 417 



and no remains whatever would be left to tell the story of the kings of the 

 forest as we see them embalmed in these specimens in their mummy-cases 

 of milk- white quartz. 



From this point of view our plant and forest remains are disposed of in 

 nature in three different ways, viz. : — 



1. They rot and mix with the soil, where the carbon slowly oxidizes in 

 the earth. This is proved by experiment. The air of the soil is found to 

 contain far more carbon dioxide than the atmosphere, and thus the C0 2 of 

 the soil is far greatest during the summer months, when the temperature is 

 high. Pettenkoffer (Watt's Client. Die. 3, Sup., p. 133) found that the 

 quantity of 0O 2 in the air of the soil increases very gradually from the 

 greatest depth examined by him — about fourteen feet — -upwards to the 

 surface, and that during August and September, at Munich, it was five 

 times greater than it was in January. This can only be from the gradual 

 oxidizing of the woody matter of the soil — at least the presumption is very 

 strong that it is so, although some are of opinion that it may be obtained 

 from some of the lowest forms of animal life. 



2. The remains of plants and trees may oxidize so gradually that, in a 

 silicious soil where they absorb silicious water, they may be silicified, and may 

 thus form vast gravel beds of quartz, or of nodules of sandstone composed 

 of quartz, lime, magnesia, potash, etc., in combination, according as the trees 

 or the vegetation were rich in these. In this way our lignite beds may 

 pass by oxidation into sandstones or slate or marl, according as the original 

 vegetation was rich in silica, alumina, or lime, and according as the water 

 absorbed by it was rich in these elements. 



3. Or these remains may — by being excluded from the atmosphere by 

 accident, or where deposited in great thickness — form beds and seams of 

 coal which may resist for a long time the oxidizing influence of the air. 

 Coal seams are almost always found to have been protected from the air 

 and from silicious water by dense beds of fireclay above and below, im- 

 pervious to water and air and other elements inducing change. These 

 deposits depending only on rare and accidental conditions will, therefore, be 

 the exception, and will be the least common way in which the carbon of 

 these remains is disposed of. 



These considerations lead us to suspect that vegetation may have had 

 more to do with the formation of many of onr sandstone rocks than is 

 generally supposed. Many things strengthen such a supposition, such as 

 the ash and plant beds so frequently met with, the eminently concretionary 

 character of many, almost all of them, and the strange absence of fossil 

 remains from many of our sandstones. The red and blue slates of our 

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