Since the dreadful blight to the potato erop of Ireland some years ago, when the entailed consequence of famine almost decimated the population of that unhappy land, agriculturists, agricultural chemists, and scientific gentlemen of all countries, have experimented upon this favorite and important esculent, with a view of ascertaining the causes, and preventing the ravages, of the potato rot. Numerous theories of its causes have been advanced, and any number of remedies proposed; but it would appear that, beyond the improvements in the selection of the seed, the cultivation of the vine, and the gathering and preserving the potato with increased care and skill, but slight benefit toward the great end sought has been derived from these sources. What the most distinguished agriculturists and savans of the world have failed to accomplish by the most intense thought and experiment, has, it appears, been effected, like the development of numerous facts in mechanics and science, by accident; or rather, such an effect was produced from this cause as set science to work in the solution of the problem, and to give it a practical tendency. A few years ago, the English papers published a statement that some boys in Belgium, for amusement, inserted peas in seed potatoes which they were planting, and that in due time both peas and potatoes grew together, producing an unustfal yield of peas. These were gathered, and the potatoes were allowed to ripen, and upon digging proved to be entirely sound, while the same sort, in other parts of the field, were badly rotten. This fact coming to the knowledge of Mr. J. Jackson, of Leeds, England, prompted him to submit a series of samples of diseased and sound potatoes to careful chemical analysis, and he invariably found that the diseased potatoes, as compared with the healthy ones, exhibited a marked deficiency of nitrogen and of nitrogen-ized matter in every instance, and also a great deficiency, as compared to the published analysis of the potato, by Liebig and others, made some years before. " From that result," ays Mr. Jackson, in his published report, " I inferred that the potato being inherently deficient in nitrogen, if it were inoculated with a substance intrinsically rich in that element, as peas are, during the mutual decomposition and chemical changes of the substances of both plants, in the process of their germination and growth, a sufficient evolution of nitrogen from the pea would take place, and be absorbed by combining with and supplying the deficiency of that element in the potato, and thus communicate, as it were, its equivalent in that way, and counteract its tendency to disease." Mr. Jackson then tried the experiment practically, by procuring several kinds of potatoes for sets whole, and inserting four or five peas (according to the size of the potato) deep into the fleshy part of the set, taking care to avoid the eye, and planting them in the usual way. The result was perfect success, with an extraordinary yield of both peas and potatoes, the latter being, almost invariably, large and healthy, and free from every trace of disease. These potatoes were laid on a wooden floor in a house, where they remained all winter, and in the following spring they were found to be all sound and healthy, and were employed as sets again in the same way, with the same result.