The State Agricultural Chemist of Maryland, Mr. Higgins, publishes a paper, showing the necessity of droughts to replenish the soil with mineral substances, carried off to the sea by the rains and also taken up by the crops, and not returned by manure. These two causes, always in operation, would, in time, render the earth a barren waste, in which no verdure would quicken, and no solitary plant take root, if there was not a natural counteraction by drought, which operates to supply this waste in the following manner. During dry weather, a continual evaporation of water takes place from the surface of the earth, which is not supplied by any from the clouds. The evaporation from the surface creates a vacuum, so far as water is concerned, which is at once filled by the water rising up from the subsoil of the land; the water from the subsoil is replaced from the next strata below, and in this manner the circulation of water in the earth is the reverse to that which takes place in wet weather. With this water also ascend the minerals held in solution, the prosphates and sulphates of lime, carbonate and silicate of potash and soda, which are deposited in the surface soil as the water evaporates, and thus restores the losses sustained as above stated.

The author of this theory appears to have taken considerable pains to verify the fact by a number of interesting experiments. The subject is worthy the attention of men of leisure and of education, who pursue the rational system of blending chemistry with agricultural science.

The above notice by the Phila. Public Ledger of Mr. Higgin's experiments, calls our attention to a well known fact, though in a somewhat new light. Practical men are well aware that a subsoiled piece of ground will hold a larger body of water in suspen-sion than it Would in its natural state, and that this moisture rises to the surface in dry weather through its tendency to endeavour to equalize its distribution through all media containing it; precisely as a dry sponge " sucks" up water from a shallow vessel. That it should take up mineral salts at the same time is so very probable " on the face of it," that it is surprising not to have occurred to our scientific agriculturists before. It will give a new turn of thought to our subsoilers.