The art of drying hops, therefore, has been a subject of speculation for many years; and although we find the kiln apparatus for preserving them differ in many places, from the various opinions of the projectors, yet they are all intended for the same mode of action, i. e. the producing of a proper degree of heat, which must be regulated according to the state of the atmosphere at the gathering season, and the consequent quantity of the watery extract that the hops contain at the time:  thus it is usual to have two kilns of different temperatures at work at the same time.  It should, however, be observed, that the principal art of drying hops is in doing it as quickly as possible, so as not to injure them in their colour.  As soon as they are dried, it is considered necessary to put them up into close and thick bags.

It should be observed, that all vegetables contain at every period of their growth two distinct species of moiture:  the one called by naturalists the common juice, which is the ascending sap, and is replete with watery particles:  the other is termed the proper juice, which having passed up through the leaves, and being there concocted and deprived of the watery part, contains the principle on which various properties and virtues of the plant depend.  We therefore find that the operations above described only go to this, that the watery particles in the common juice should be evaporated, as being a part necessary to be got rid of; and the proper juice being of a volatile nature, the less time the plants are exposed for that purpose, the less of this precious material will be lost:  and as those parts are flying off continually from all dried vegetables, there should be one general rule made with regard to their peparation; for, if we instance mint, balm, pennyroyal, &c., the longer these are kept in the open air, the weaker are they found to be in their several parts.

From hence we may naturally infer, that the usual mode in which the generality of herbs are dried, is not so good for the purpose, as one would be if contrived on similar principles, as, during the length of time necessary for the purpose, a great deal of the principal parts of the plants must of course be evaporated and lost; for little else is regarded than to dry them so as to prevent putrefaction.  Although the generality of herbs met with are prepared as above described, yet in such articles as Digitalis, Hyoscyamus, Conium, Toxicodendron, &c., where the quantity necessary for a dose is so small, and so much depends on its action, practitioners are often obliged to prepare it themselves.  I shall therefore relate the following mode as the best adapted to that purpose.  The Digitalis is prepared by collecting the leaves in the summer, and stripping them off from the foot-stalks; these should be then carefully exposed to a slow heat, and the watery extract slowly thrown off; in which they should not be exposed to any great degree of heat, which