We have before referred to Mr. Ruffin as the publisher, more than twenty years ago, of "Elkington's Theory and Practice of Draining, &c., by Johnstone;" and we find in his recent essays, evidence of how thoroughly practical he has made the system of Elkington in his own State. Indeed, we know of no other American writer who records any instance of marked success in the use of Elkington's peculiar idea of releasing pent up waters by boring. Mr. Ruffin, however, has applied, with great success, this principle of operation, to the saturated sand-beds which underlie the tracts of low land in his district of country. These water-beds in the sand lie at depths varying usually from four to eight feet below the surface. This surface stratum is comparatively compact, and very slowly pervious to water before it is drained. The water from below, is constantly pressing slowly up through it, of course preventing any downward percolation of the rain-water. By running deep drains at wide intervals, and boring down through this surface stratum with an auger, the pent up water below finds vent and gushes up in copious springs through the holes, and flows off without coming nearer to the surface than the bottom of the drains; thus relieving the pressure upward, and lowering the water-line in proportion to the depth of the drains. Mr. Ruffin gives an instance of the drying up of a well half a mile distant, by cutting a deep drain into this sand-bed, and thus lowering its water-line. No doubt in many localities in our country, a competent geological knowledge may detect formations where this principle of drainage may be applied with perfect success, and with great economy. _Is there danger of over-draining swamp lands?_ In speaking of the injury by drainage, we have treated of this question. Our conclusions may be briefly stated here. There is an impression among English writers, that light peaty soils may be too much drained; but many distinguished drainers doubt the proposition. No doubt there are soils too porous and light to be productive, when first drained. They may require a season or two to become compact, and may require sand, or clay, or gravel, to give them the requisite density; but these soils would, we believe, be usually unproductive if shallow drained. In short, our idea is, that, in general, a soil so constituted as to be productive under any circumstances, will retain, by attraction, moisture enough for the crops, though intersected by four-foot drains at usual distances; and that cold water pumped up to the roots from a stagnant pool at the bottom, is not, either in nature or art, a successful method of irrigation.