The saturation often falls to 30 per cent., but with great variability. Evaporation goes on most rapidly when the per centage of saturation is lowest; and, as before observed, the cause of the excess of evaporation in this country over that of England is the excessive humidity of that climate and the dryness of this. It has also been said that there is greater need for drainage in the United States on this account; and, as the warmth induced by draining is somewhat, in its effect, a merchantable product, it may be well to consider it for a moment in that light. First: The drained land comes into condition for working, a week or ten days earlier in the Spring than other lands. Secondly: The growth of the crops is quickened all through the Summer by an increase of several degrees in the temperature of the soil. Thirdly: The injurious effects of frost are kept off several days later in the Fall. Of the value of these conditions, the farmer, who has lost his crops for lack of a few more warm days, may make his own estimates. In Roxbury, Mr. I. P. Rand heats up a portion of his land, for the purpose of raising early plants for the market, by means of hot water carried by iron pipes under the surface of the ground. In this manner he heats an area equal to 100 feet by 12 feet, by burning about one ton of coal a month. The increase of temperature which, in this case, is caused by that amount of coal, can, in the absence of direct measurement, only be estimated; but it, probably, will average about 30 deg., day and night, throughout the month. In an acre the area is 36.4 times as great as that heated by one ton of coal; the cost being in direct proportion to the area, 36.4 tons of coal would be required to heat an acre; which, at $6 per ton, would cost $217.40. To heat an acre through 10 deg., would cost, then, $72.47. It may be of interest to consider how much coal would be required to evaporate from an undrained field that amount of water which might be carried off by under-drains, but which, without them, is evaporated from the surface. It may be taken as an approximate estimate, that the evaporation from the surface of an undrained retentive field, is equal to two inches vertical depth of water for each of the months of May, June, July, and August; which is equal to fifty-four thousand three hundred and five gallons, or eight hundred and sixty-two hogsheads per acre for each month. If this quantity of water were evaporated by means of a coal fire, about 22-2/3 tons of coal would be consumed, which, at $6 a ton, would cost $136. The cost of evaporating the amount of water which would pass off in one day from an acre would be about $4.53. It is probable that about half as much water would be evaporated from thorough-drained land, though, by some experiments, the proportion has been made greater--in which case the loss of heat resulting from an excess of moisture evaporated from undrained retentive land, over that