412 Relatio7is between Geological Strata aiid 



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-r 

 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 earthy base and a little volatile oil, except water. 

 It would seem natural, therefore, to conclude that 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 debris it discharges through rivers, valleys, and hills, 

 under the influence of drainage and frost, f 



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 grit ! and how 

 various the irregularities of course in streams traversing a bold 

 primitive range, or a craggy 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 

 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. 



-j- Secondary sand brought down by rivers hinders, primary sand pro- 

 motes, vegetation. 



