412 Relations between Geological Strata and 
2. Nor is it so unreasonable to expect that the elements of 
merely silica, alumina, magnesia, and lime, with vegetable 
and animal impregnations, should afford a test of the pro- 
ductions peculiar to them. From six elements how numerous 
may be the combinations, when it is recollected that any one 
of them will form a soil sufficient to support many plants !* 
For if these elements are few and simple, equally simple is 
the structure of vegetable frames. According to the experi- 
ments of Geoffroy and Tournefort, all vegetables yielded only 
a very slight ear thy base and a little volatile oil, except water. 
It would seem natural, therefore, to conclude chat each simple 
element has its appropriate plants, which feed on it, besides 
the numerous others which partake of its nutritious particles 
in a state of combination. 
3. It is not unreasonable to suppose that the substratum of 
each district has extensive influence over the soil lying on it, 
by the débris it discharges through rivers, valleys, and hills, 
under the influence of drainage and frost. + 
4, Since it is not contrary to reason to conclude that the 
soil is dependent on the stratification; so is it reasonable to 
conclude, that the climate is greatly modified by the same 
cause. ‘The peaks of mountains, it is well known, attract rain ; 
and level strata, such as our new red sandstone, retain moisture 
long on their surfaces in the various forms of pools, rivers, and 
marshes. ‘The porousness, clefty form, or closeness of the 
mass of the rocks themselves must, we should therefore pre- 
sume, greatly modify the climate by the drainage they obstruct 
or promote, and the heat they produce from reflection. How 
different the heat of a basalt or smooth granite rock from that 
of rough limestone, or red sandstone, or ‘ragged erit ! and how 
various the irregularities of course in streams traversing a bold 
primitive range, or a cragey transition, or a level pavement of 
secondary rock! Now plants are the most sensitive things 
alive ; they are the most perfect barometers, and register every 
change, even the slightest, in the temperature and moisture in 
the atmosphere. ‘They are shutting up their lovely petals 
when the sun reaches certain elevations in the heavens; and 
they are drooping their heads, and closing even their large 
5 
fleshy leaves, at the approach of a change, even when the ther- 
* As there are transition rocks, so there are transition plants found in the 
primitive and transition districts equally, or in the transition and secondary 
equally, or in the secondary and alluvial equally. It is contended, how- 
ever, that the same plants do not thrive equally in districts widely dissimilar 
in geological structure. 
+ Secondary sand brought down by rivers hinders, primary sand _ pro- 
motes, vegetation. 
