Adhesion of Iron Nails, in which Mr. Bevan's object was to determine, first, the adhesive force of different kinds of nails, when driven into wood of different species: second, the actual weight, without impulse, necessary to force a nail a given depth; third, the force requisite to extract a nail when so driven. Mr. Bevan observes, that the theoretical investigation points out an inequality of resistance to the entrance and extraction of a nail, supposing the thickness to be invariable; but as the general shape of nails is tapering towards their points, the resistance of entrance necessarily becomes greater than that of extraction; in some experiments he found the ratio to be about 6 to 5. The following Table exhibits the relative adhesion of nails of various kinds when driven into dry Christiana deal, at right angles to the grain of the wood.

The percussive force required to drive the common sixpenny nail to the depth of 11/2 inch into dry Christiana deal, with a cast-iron weight of 6.275 lbs. was four blows or strokes falling freely the space of 12 inches; and the steady pressure to produce the same effect, was 400 lbs. A sixpenny nail driven into dry elm, to the depth of one inch across the grain, required a pressure of 327 lbs. to extract it; and the same nail driven endways or longitudinally into the same wood, was extracted with a force of 2571bs. The same nail driven 2 inches endways into dry Christiana deal, was drawn by a force of 257lbs.; and to draw out 1 inch, under like circumstances, took 87 lbs. only. The relative adhesion, therefore, in the same wood, when driven transversely and longitudinally, is 100 to 78, or about 4 to 3 in dry elm, and 100 to 46, or about 2 to 1 in deal; and in like circumstances, the relative adhesion to elm and deal is as 2 or 3 to 1. The progressive depths of a sixpenny nail into dry Christiana deal, by simple pressure, were as follows: -

in the above experiments, great care was taken by Mr. Bevan to apply the weights steadily, and towards the conclusion of each experiment, the additions did not exceed 10 lbs. at one time, with a moderate interval between, generally about one minute, sometimes ten or twenty minutes. In other species of wood, the requisite force to extract the nail was different. Thus, to extract a common sixpenny nail, from a depth of one inch, out of

From these experiments, we may infer that a common sixpenny nail driven two inches into dry oak, would require a force of more than half a ton to extract it by a steady force.