vented their general introduction into Europe, notwithſtanding the moſt undoubted proofs of their utility have been given. But mankind can with difficulty be brought to lay aſide eſtabliſhed practices, or to adopt new ones. And perhaps we have more reaſon to be ſurpriſed that a practice, however rational, which was propoſed about forty years ago, ſhould in that time have been adopted in ſo many places, than that it has not univerſally prevailed. It is only by degrees that the great body of mankind can be led into new practices, however ſalutary their tendency. It is now nearly eighty years ſince inoculation was introduced into Europe and America; and it is ſo far from being general at preſent, that it will, perhaps, require one or two centuries to render it ſo.
In the year 1745, Franklin publiſhed an account of his new-invented Pennſylvania fireplaces, in which he minutely and accurately ſtates the advantages and diſadvantages of different kinds of fire-places; and endeavours to ſhew that the one which he deſcribes is to be preferred to any other. This contrivance has given rife to open ſtoves now in general uſe, which however differ from it in conſtruction, particularly in not having an air-box at the back, through which a conſtant ſupply of air, warmed in its paſſage, is thrown into the room. The advantages or this are, that as a ſtream of warm air is continually flowing into the room, leſs fuel is neceſſary to preſerve a proper temperature, and the room may be ſo tightened as that no air may enter through cracks; the conſequences of which are colds, tooth-aches, &c.
Although philoſophy was a principal object of Franklin's purſuit for ſeveral years, he confined himſelf not to this. In the year 1747, he became
