The Pharmacist, of Chicago, referring to the letter of our English correspondent on the cause of the potato rot, takes some exception to the exclusive use of the term "practical men" by the potato grower, in connection with the discovery of the cause of the disease. It is the one who takes his microscope and looks into the matter to see what is actually there, and notes what is doing the work, that should be called the practical man, - while it is one who does not do this, but places his guesses in the place of practical observation, that should be dubbed the mere theorist. "Decay does not come about of itself," says the author of the criticism, "something does cause decay, - and if it is not the small fungus, Peronospora infestans, it must be caused by something else. To say that disease is caused by a weakened vital power will not do. Weakened vital power may invite disease, but what is disease?" and the author suggests that if not in the nature of Peronospora, then it is probably Bacteria. They may cause the disease; and the Peronospora may follow.

Though thus criticising, he on the whole commends the communication of our correspondent.