1. Transactions of the Society of Arts, 1819, p. 116. 2. The contrivance is due to Mr Hencky, of High Holborn, in whose establishment it is in constant use. 3. About seven or eight years since, without being aware of Sir David Brewster's proposal. I adapted a barometer, as a pendulum, to the works of a common eight day clock: it remained in my library for several months, but I have mislaid the observations which were made. 4. Memoires de l'Academie des Sciences de Petersburgh, 6e serie, tom. i. p. 4. Chapter 9 Economy of the Materials Employed 77. The precision with which all operations by machinery are executed, and the exact similarity of the articles thus made, produce a degree of economy in the consumption of the raw material which is, in some cases, of great importance. The earliest mode of cutting the trunk of a tree into planks, was by the use of the hatchet or the adze. It might, perhaps, be first split into three or four portions, and then each portion was reduced to a uniform surface by those instruments. With such means the quantity of plank produced would probably not equal the quantity of the raw material wasted by the process: and, if the planks were thin, would certainly fall far short of it. An improved tool, completely reverses the case: in converting a tree into thick planks, the saw causes a waste of a very small fractional part; and even in reducing it to planks of only an inch in thickness, does not waste more than an eighth part of the raw material. When the thickness of the plank is still further reduced, as is the case in cutting wood for veneering, the quantity of material destroyed again begins to bear a considerable proportion to that which is used; and hence circular saws, having a very thin blade, have been employed for such purposes. In order to economize still further the more valuable woods, Mr Brunel contrived a machine which, by a system of blades, cut off the veneer in a continuous shaving, thus rendering the whole of the piece of timber available.