eee er” 
218 
then at rate 2A it could move a body of 64 Ibs. weight. If again its velocity be 
trebled its motor power is increased 729 times. 
Again, it has been observed that water moving at the rate of 
3 Inches in a sec. tears up Fine Clay. 
6 ” ” ” Fine Sand. 
12 fe by ; Fine Gravel. 
36 5 A 5» Large Gravel. 
Carrying the above laws in our mind it is apparent that if any alteration in 
the velocity of a stream takes place the positions where the several bodies, viz., 
gravel large and small, sand and clay, were deposited will be materially altered, 
and very probably if the velocity is increased large gravel will be borne away and 
deposited where formerly only fine clay reached, and if velocity be diminished the 
fine clay might be deposited where formerly the gravel was. 
Thus we see by the motor power of water the superposition of beds of 
materials of different densities can be accounted for ; how, for instance, a bed of 
large gravel may be found above a bed of fine clay. In still water, of course, the 
heavier materials will always form the lowest beds. 
With reference to the third case, it is easy to understand how streams 
passing through and over rocks of a varied composition will carry away detritus of a 
mixed composition, and if the materials be of the same density they will be deposited 
somewhere or other in the same bed, and form a mixed soil. Soils of this descrip- 
tion are much the most common and I may add much the most desirable. 
With regard to this most interesting subject, viz., the power and effects of 
water in modifying this earth’s surface, I must refer you to some of the standard 
works on Geology, such as Sir C. Lyells, and others, where you will find abundant 
examples of cases of which I have spoken above, besides other interesting matter. 
But it is impossible for me in a short paper to dwell longer on this part of our 
subject, I will therefore now pass on to the second mode of action of water, 
namely the Chemical action. 
Water has the power of holding in solution various substances, such as 
mineral salts, as Bicarbonate of Lime, Hydrated Lime, Chloride of Sodium— 
common salt, Chloride of Magnesium, and many others. These substances, 
derived chiefly from the decay of volcanic rocks, are taken up by water and 
carried away to be mingled with other soils. On evaporation of the water, these 
substances are left in the soil and again rendered soluble by rain, and in that state 
taken up and assimilated by plants. This power of water is of the highest impor- 
tance with reference to the fertility of soils, for no soil is fruitful without the pre- 
sence of some at least of these mineral salts. 
Many hard rocks, as well as soft soils, owe their origin to this chemical 
power jof water; the most notable of these stony deposits are the Travertins of 
Italy and elsewhere. This Travertin is a rock generally of whitish grey or yellow 
color, very hard, and composed entirely of Carbonate of Lime, pure limestones 
