and the Storage of Water. 
59 
from which it falls. The product of these two during the space 
of one minute, divided by 33,000, gives the horse-power. The 
weight of a cubic foot of water is generally taken at 62'5 lbs., 
and contains 6*23 gallons. For example, a stream yielding 
60 cubic feet a minute, and falling 30 feet, would give 3"4 horse- 
power ^^-^ slooo^'^^j^ ^"^ ^^""^ deduction has 
to be made for friction and waste to obtain the actual power, 
this being more or less according to the construction of the 
engine. For a well-made turbine, 20 per cent, may be sufficient ; 
whereas for an undershot wheel, 70 per cent, should be allowed. 
Conclusion. 
In all the works of Nature the means are most beautifully 
adapted to the end to be accomplished, and everything follows a 
regular law and order. Thus with the rainfall and water-supply : 
the sun by its heat causes the vapour to rise from the surface 
of the ocean ; the winds carry the vapour across the land ; the 
clouds are caught in their progress by the mountain-tops, or they 
come in contact with a cooler stratum of atmosphere, when con- 
densation takes place and the vapour falls to the earth in the form 
of rain, affording a supply of a requisite indispensably necessary 
for all animal and vegetable life. By the force of gravity the water 
not taken up by the vegetation sinks through the pores of the 
soil and gradually percolates to channels formed in the hollows 
of the surface of the earth. Along these it runs till it is finally 
discharged back into the ocean. The process of percolation 
through the soil is so slow, that the abundance of one season is 
sufficient to keep up a supply for the drought of another. The 
increase of population and the growing wants of civilisation 
compel the inhabitants of a thickly populated country to obtain 
the greatest amount of food-supply that is possible from the soil, 
and by artificial means to stimulate production. Of the several 
processes conducive to this end, one of the most successful is the 
drainage of the land by pipes. This, by removing the water more 
rapidly than the slow operations of nature would accomplish it, 
opens the pores of the soil and affords a supply of air to the roots 
of the plants; and also, by checking surface-evaporation, increases 
the temperature of the soil. So great has the benefit derived from 
under-drainage been found, that it has been generally adopted 
without reference to the effect that this interference with the 
operations of nature would cause. The result has been floods at 
one time and droughts at another. In the zeal for the removal of 
water, no regard has been paid to the regulating process of nature 
for the storing up the abundance of one season for the wants 
