We have all of us our favorite theories on particular subjects; and there are few people who have not cherished one of their own concerning that precious esculent, the potato, and its mysterious " disease." Having arrived at last at a crop of theories on the subject as multiform as the varieties to which that singular root itself has yielded in the progress of cultivation - and it yields a number from the seed of every plant - the bewildered public will be scarcely less glad of the chance of escaping from it altogether to a new and preferable substitute, than they would be of the actual discovery of a remedy for the formidable disease by which it is afflicted. To the French - who are, next after the Chinese, perhaps the best and most enterprising as, difficulties considered, they are doubtless the most successful gardening husbandmen in the world - we are indebted for the fairest prospect of this refuge from potato famine that has yet been propounded. We would not be ungrateful to the potato, and could not find it in our heart to despise it; and if we are about to relinquish it, diseased or not, we could only consent to renounce the root for a better. Cobbett's rash abhorrence of it was political.

He did not understand its history ; and we may be allowed to say its history, notwithstanding the amusing anecdotes with which it teems, has always been misunderstood. Thus if the Irish adored, and adore it> they had the moot undoubted right Turn to any work of general information that we like, the attempt is constantly made to deprive Ireland of the glory of giving the potato to Europe - on its introduction from " Old Virginny," in 1584, by Sir Walter Raleigh - because the name given it by the Spaniards, " battata," is a corruption of some name given it by the inhabitants of Guito; and because we directly derive our name "potato" from that which was applied to a root grown previously in the gardens of Spain and Portugal. Now this is all erroneous. It was a convolvulus - the Spanish sweet potato - which in the beginning of the sixteenth century was introduced into Spain, and cultivated under the Indian name of battata. Old Gerrard, our famous English herbalist, knew this very well, and sets us all right.

In 1590 he describes the potato (convolvulus) roots as " common and ordinary meat among Spaniards, Italians, and many other nations; which," says he, " no doubt are of mightie nourishing parts, and so strengthen and comfort nature; whose nutriment is, as it were, a mean between flesh and fruit, though somewhat windy; but being roasted in the embers, they do lose much of their windiness, especially being eaten sopped in wine. Of these roots may be made conserves, no leas toothsome, wholesome, and daintie than of the flesh of quinces ; and likewise those com. fortable and delicate meates called in shops morcelli, plancentulae, and divers others such like. These roots may serve as a ground whereon the cunning confectioner or sugar-baker may worke and frame many comfortable and delicate conserves and restorative sweetmeats." Even so, Shakespeare - who, by-the-bye, has been noted as ignoring Raleigh and all his works, and never once mentions tobacco, although Ben Jonson often does - makes Falstaff, in allusion to the sweet convolvulus, say, in the "Merry Wives of Windsor" -

"Let it rain potatoes, and hail kissing comfits;" and it is evident that the connection of the meteorological phenomena thus invoked would be unintelligible with reference to the potato; whilst it is obvious enough, from what Gerrard says, that kissing-comfits and all such sweets were made of the Spanish potato. Evelyn was urged by the Royal Society to treat of their cultivation in his " Sylva," published under its direction; and it is not a little remarkable, in connection with what we are about to mention respecting the new Chinese potato, the probable successor of the Virginian, that he recommended exactly the course which is not found advantageous in the case of the latter, but is nevertheless indicated as the means of rendering the new root most productive, namely, to leave the parent plants in the same spot of ground from year to year, covered up with litter to shield them from the winter's frost, and only abstracting a few tubers for use in the autumn.

Although the calamity which has descended on the heads of these potato-eating millions, by the failure of the root of their dependence, has superadded to the picture a strange phasis of alteration, it would be no product of ordinary pretensions by which we could ever expect to see it superceded. Yet it would be a still greater blessing to Ireland, if a substitute less incident to this alarming casualty could be introduced; for the latest accounts of the 400,000 annual outpourings of the exodus to New York is couched in the prayer of a Transatlantic Hibernian to the Times, like that of the French paterfamilias on the increase of his olive branches, " to put a stop to dis," since sickness and destitution threaten their annihilation, even in the land of refuge. Well, the new Chinese potato, or Dioscorea batatas, is alleged to be the substitute required.

This new potato was, several years since, transmitted, along with other useful and promising agricultural plants, by M. de Mon-tigny, who is consul for France at the Port of Shanghai, in Northern China, The name which he bestowed upon it was that of Dios-corea japonica; but it has been considered by Professor Decaisne, of the Parisian Museum of Natural History (Jardin des plantes), and acknowledged by Professor Lindley and others, that Dioscorea batatas would not only be a more popular and familiar, but a more appropriate name, seeing that although the plant may in its origin be Japanese, of its cultivation in that dark interior we know literally nothing; whilst its culture in the northern parts of China, and in latitudes assimilated to our own in point of climate, being a fact quite accessible in all its details, ought not to be submerged under the name that associates it with the very exclusive territory of Japan. The plant, or rather tuber, is doubtless a Dioscorea, or yam; and yams in general are tropical productions. The various species - D. alata, sa-tiva, and aculeata - yield tubers, which in warm countries are substituted for the potato, and the order is accused of combining with the farinaceous matter existing in its tubers a prevalent acridity, which is sometimes even purgative.