Hawrpros.— 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 i 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 CO, of 
the soil is far greatest during the summer months, when the temperature is 
high. Pettenkoffer (Watt's Chem. Dic. 8, Sup., p. 183) found that the 
quantity of CO, in the air of the soil inereases 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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