f 
THE SCIENTIFIC HISTORY OF A PLANT. Ill 
2> as is the case in the luxuriant orchards of Herefordshire, there is much fertility. The pure formation 
is very barren — the summits of its mountains being covered with snow. 
The Carboniferous System, including the mountain limestone and the millstone-grit, does not form a 
son of the carbonifc- good agricultural soil ; millstone-grit is usually at the surface of barren elevated 
moorlands, covered with mountain peat : here mosses flourish well on these elevated 
moors : it may be that the millstone-grit affords a congenial soil for them. 
The mountainous limestone soil is, generally speaking-, in an unimproved condition ; yet the debris 
Mineral contents. in some cases produces good pasture land. On the whole we cannot complain of the 
carboniferous system — even if its agricultural character is not so veiy valuable — when its annual 
mineral wealth is estimated at more than £19,520,000 pounds sterling. 
The New Red Sandstone, upper and lower, is most bountiful to us : its mineral contents being rock 
Sou of the new red sa ^, gypsum, heavy spar, and copper ; and, with all this, it furnishes us with the 
sandstone, richest land in England — fertile for wheat and beans, and producing very fine cider. 
In the Lias, and its shales, marls, clays, rocks, we have much agricultural diversity — from the cold 
Sou or the lias. wet tenacious soil, which is produced from the blue clay, to the vigorous fertile land 
composed of clayey loam. In the upper part of the lias, where the sands of the inferior oolite rest 
upon it, they may be sometimes turned in and mixed with advantage. The has forms extensive pasture 
lands in Somersetshire and Warwickshire. 
To understand the very great diversity of soil which is found in the Oolite formation, we must take 
Sous of the oolite. into account its different divisions — its three primary, and eight sub-divisions. The 
soil of the upper oolit* is perhaps the most difficult to bring into a good state of cultivation, yet it 
affords some very beautiful woodland scenery in Oxfordshire and Northamptonshire. 
The lower greensand beds of the Cretaceous formation, are very rich and capable of the highest 
sous of the cretaceous cultivation. The chalk downs, with then' short sweet grass that feeds so many sheep, 
formation. belong to the upper chalk ; the lower beds of which, when mixed with alumina, are 
converted into a rich and valuable marl : the productive upper greensand gives this marl : in Bedford- 
shire the lower greensand is extremely rich. 
In generally noticing the Tertiary beds, we do not make any distinction between the Eocene, Miocene, 
soils of the tertiary Pliocene, and the Glacial period ; including in them what does not rightly belong to 
beds are very various. them, the alluvium and the diluvium. We look upon this modern scries as epitomised 
in the London and Hampshire veins — as partially also exhibited in Norfolk and Suffolk. In these 
beds we have clay, gravel, and sand. It is obvious that gravel must form a poor worthless soil, while 
clay forms a very cold one ; yet, when these substances arc intermixed, they produce valuable and 
fertile arable land. It must be quite apparent that all these soils are more or less influenced by the 
physical conformations of the country in which they are situated. 
Just now I spoke of soils doing more than simply supplying certain inorganic constituents to plants. 
I refer to the fact that by so doing they did something else than influence the geographical distribution 
of their species, genera, and families. 
In merely a geological survey of a soil we arc apt to underestimate, if not to overlook, the important 
water largely iniiu- RlL ' r ' which is played by water in vegetation. Yet, if we cast our eyes over a hydro- 
onces geographical dis- graphic map of the world, we find certain rainless districts, destitute of water courses, 
and where the ah - is rarified to allow of the condensation of aqueous vapour. What do 
travellers tell us of the vegetation of a tract of country so circumstanced ? Why, in this rainless desert 
let but a little spring of water rise, it generates fertility in the limited sphere of its operations; an 
oasis is produced ; and that arid ocean of burning sand rejoices in one small island of vegetable 
life. 
Water is one local cause of influencing the fertility of a soil, but there are various others, many 
Local cause, iniiuen- physical actions in one place shifting the superficial detritus which covers the 
dngftofc distribution, more stubborn rocks; ami if we do not take circumstances like these into account, we 
shall be apt to consider that geology gives us more information than it really dues : to form the idea, 
that witli a geological map before us.it would be no trouble by its inspection accurately to ascertain 
the suil of any particular country. 
The millstone-grit plains around Paris in a geological map of the district, would lie similarly 
Example of ono of coloured; yet each one of these plains has its own particular form of vegetation. 
Hum local Oram. Montmorency is covered with corn fields ; Sannois supports only a short sterile rod i 
Meudon is furnished with Spanish chestnut trees; the Aira Bexuosa, tin' M lampyrum sylvaticum, the 
l'tiiis aquilina, all grow there. Only a minute's inspection clears up this seeming incongruity, Wfi 
find, though no difference is pointed out by the map — for geological!} speaking, there can be no 
