taking out the upper bar, and replacing it when they are in. The round figure of the fire, when thoroughly kindled, is agreeable. It represents the Great Giver of warmth to our system. As it burns down and leaves a vacancy above, which you would fill with fresh coals, the upper bar is to be taken out, and afterwards replaced. The fresh coals, while the grate continues in the same position, will throw up as usual a body of thick smoke. But every one accustomed to coal fires in common grates must have observed, that pieces of fresh coal stuck in below among the red coals have their smoke so heated, as that it becomes flame as fast as it is produced, which flame rises among the coals and enlivens the appearance of the fire. Here then is the use of this swivel grate. By a push with your tongs or poker, you turn it on its pin till it faces the back of the chimney, then turn it over on its axis gently till it again faces the room, whereby all the fresh coals will be found under the live coals, and the greater part of the smoke arising from the fresh coals will, in its passage through the live ones, be heated so as to be converted into flame; whence you have much more heat from them, and your red coals are longer preserved from consuming. I conceive this construction, though not so complete a consumer of all the smoke as the vase, yet to be fitter for common use, and very advantageous. It gives too a full sight of the fire, always a pleasing object, which we have not in the other. It may with a touch be turned more or less from any one of the company, that desires to have less of its heat, or presented full to one just come out of the cold. And, supported in a horizontal position, a tea kettle may be boiled on it.

The author's description of his Pennsylvania fireplace, first published in 1744, having fallen into the

hands of workmen in Europe, who did not, it seems, well comprehend the principles of that machine, it was much disfigured in their imitations of it; and one of its main intentions, that of admitting a sufficient quantity of fresh air warmed in entering through the airbox, nearly defeated, by a pretended improvement, in lessening its passages to make more room for coals in a grate. On pretence of such improvements, they obtained patents for the invention, and for a while made great profit by the sale, till the public became sensible of that defect in the expected operation. If the same thing should be attempted with this vase stove, it will be well for the buyer to examine thoroughly such pretended improvements, lest, being the mere productions of ignorance, they diminish or defeat the advantages of the machine, and produce inconvenience and disappointment.

The method of burning smoke, by obliging it to descend through hot coals, may be of great use in heating the walls of a hot-house. In the common way, the horizontal passages or flues that are made to go and return in those walls, lose a great deal of their effect when they come to be foul with soot; for a thick blanket-like lining of soot prevents much of the hot air from touching and heating the brick work in its passage, so that more fire must be made as the flue grows fouler; but by burning the smoke they are kept always clean. The same method may also be of great advanvage to those businesses, in which large coppers or caldrons are to be heated.

Description of an Instrument for taking down Books from high Shelves.

January, 1786.

Old men find it inconvenient to mount a ladder or steps for that purpose, their heads being sometimes subject to giddinesses, and their activity, with the steadiness of their joints, being abated by age; besides the trouble of removing the steps every time a book is wanted from a different part of their library.

For a remedy, I have lately made the following simple machine, which I call the Long Arm.

A B, the Arm, is a stick of pine, an inch square and 8 feet long. C, D, the Thumb and Finger, are two pieces of ash lath, an inch and half wide, and a quarter of an inch thick. These are fixed by wood screws on opposite sides of the end A of the arm A B; the finger D being longer and standing out an inch and half farther than the thumb C. The outside of the ends of these laths are pared off sloping and thin, that they may more easily enter between books that stand together on a shelf. Two small holes are bored through them at i, k. E F, the sinew, is a cord of the size of a small goosequill, with a loop at one end. When applied to the machine it passes through the two laths, and is stopped by a knot in its other end behind the longest at k. The hole at i is nearer the end of the arm than that at k, about an inch. A number of knots are also on the oord, distant three or four inches from each other.

To use this instrument; put one hand into the loop, and draw the sinew straight down the side of the arm; then enter the end of the finger between the book you would take down and that which is next to it. The