No. 200.] 
to supply the wants of the vegetable kingdom, as it enters directly into 
the vascular system. 
3d. The substratum influences greatly, the productiveness of soil. 
If it is a tenaceous clay, it will be too wet and cold. The natural pro- 
ductions of such soils, are coarse grasses, such as the caries and cype- 
roideae, which are of but little value to cattle; and woody plants, whose 
stems are small, as the alders and birches, all of which are useless for 
fuel. This is a defect, which cannot, of course, be obviated by manur- 
ing. Such a soil retains with tenacity, a certain quantity of water, ge- 
nerally to saturation, and at the same time suffers the falling showers to 
pass over it without penetratinsj to much depth, or holds it in the soil 
above, if the outward drainage is insufficient, forming under these cir- 
cumstances a condition unfit for tillage. The evaporation from the sur- 
face of marshy districts, preserves the temperature in a low state; a 
state to which some vegetables are fitted constitutionally, but to which 
others, the more useful, can never adapt themselves. 
4th. Elevation. The diminished effect of the sun's rays, together 
with the exposure to winds in elevated districts, prevents the develop- 
ment of vegetable forms, and at certain points vegetation ceases from 
want of heat. The most useful vegetables cease to flourish, and come 
maturity far below the line of perpetual frost. In this latitude, corn 
and some other vegetables will not come to maturity at 1,500 feet 
above tide. The influence of latitude is the same as elevation. 
There are three other points on which I will dwell for a moment. 
The first is, how a soil naturally good may deteriorate; and the second, 
how it is to be restored; and third, how a soil defective in certain points 
is to be treated. 
1st. A soil may deteriorate by the consumption of one or more alka- 
line earths it contains, as lime or magnesia. This is more likely to 
occur on lands from which the crops are removed, and which are in a 
high state of cultivation. This may be especially true, where the crop 
has been of wheat or potatoes for a succession of years. 
2d. Constant cultivation has a tendency to reduce the soil to an im- 
palpable state, or it will become in time, without the application of pro- 
per correctives, too compact. 
3d. Cultivated lands, or those under the plough especially, are ex- 
posed to washing, by which that portion of the soil in a state fit for 
