It is very fortunate for us, that our Spring showers are not of ether; for then, instead of thawing, our land would freeze the harder! The heat of the blood is about 98 deg.; yet man can endure a heat of many degrees more, and even labor under a Summer sun, which would raise the thermometer to 130 deg., without the temperature of his blood being materially affected, and it is because of perspiration, which absorbs the surplus heat, or, in other words, creates cold. It is said, too, that on the same principle, if two saucers, one filled with water warm enough to give off visible vapor, the other filled with water just from the well, are exposed in a sharp frosty morning, that filled with the warm water will exhibit ice soonest. Wine is cooled by evaporation, by wrapping the bottle in wet flannel, and exposing it to the air. If, after all this, any one doubts the fact that evaporation tends to produce cold, let him countenance his skepticism, by wetting his face with warm water, and going into the air in a Winter's day, and his faith will be greatly strengthened. We have, in the northern part of America, most water in the soil in the Spring of the year, just at the time when we most need a genial warmth to promote germination. If land is well drained, this water sinks downward, and runs away in the drains, instead of passing upward by evaporation. Drainage, therefore, diminishes evaporation simply by removing the surplus snow and rain-water by filtration. It thus raises the temperature of the soil in that part of the season, when water is flowing from the drains; but, in the heat of Summer, the influence of the showers which refresh without saturating the soil, and are retained in it by attraction, is not lessened. As a good soil retains by attraction about one-half its weight of water that cannot be drained out, there can be no reasonable apprehension that the "gentle Summer showers" will be wasted by filtration, even upon thorough-drained land, while an avenue is open, by the drains, for the escape of drowning floods. To show the general effect of drainage, in raising the temperature of wet lands in Summer, the following statement of Mr. Parkes is valuable. An elevation of the temperature of the subsoil ten degrees, will be seen to be very material, when we consider that Indian corn will not vegetate at all at 53 deg., but will start at once at 63 deg., 55 deg. being its lowest point of germination: