"This machine," Mr. Eastman says, "furnishes a new method of manufac turing lumber for various useful purposes. Though the circular saw had pre viously been in operation in this country, and in Europe, for cutting small stuff, it had not, with the knowledge of the writer, been successfully applied to solids of great depth; to effect which, the use of section-teeth are almost indispensable.
" In my first attempts to employ the circular saw, for the purpose of manu facturing clap boards, I used one nearly full of teeth, for cutting five or six in depth, into fine logs. The operation required a degree of power almost im possible to be obtained with the use of a band ; the heat caused the plate to expand, and the saw to warp, or as it is termed, get out of true.' To obviate these difficulties, I had recourse to the use of section-teeth, and the improvement completely succeeded. The power required to perform a given quantity of work by the former method, was by this diminished at least three quarters. The work, formerly performed by seventy or eighty teeth, was, by the last method, performed by eight teeth ; the saw-dust, which before had been reduced to the fineness of meal, was coarser, but the surface of the lumber, much smoother than when cut with the full-teethed saw. The teeth are made in the form of a hawk's bill, and cut the log up, or from the circumference to the centre. The saw may be carried by an eight-inch band, and when driven a proper speed (which is from ten to twelve hundred times per minute) will cut nine or ten inches in depth into the hardest white oak timber with the greatest ease. The sappers, at the same time, cut off from one to two inches of the -sap, and straiAten the thick edges of the lumber.
'he facility with which this saw will cut into such hard materials, may be supposed to result from the well established principle, that where two substances in motion, come in contact, their respective action on each other is in direct proportion to their respective velocities ; thus, a circular plate of iron put into a quick rotary motion, will, with great ease, penetrate hardened steel, or cut through a file when applied to its circumference ; and the same principle is applicable to a saw for wood. The requisite degree of velocity is obtained by the continuous motion of the circular saw, by which also it has greatly the advantage of one that has but a slow motion, on account of dulling; as the teeth are but little affected, and being only eight in number, but a few moments' labour is requited to sharpen them. If the velocity of the saw were slackened to a speed of but forty or fifty per minute, it would require at least four such bands to carry it through a log• as above described.
One machine will cut from eighteen to twenty hundred of square feet of pine timber per day, and two of them may be driven by a common tub-wheel, seven or eight feet in diameter, having six or seven feet head of water, with a cog wheel and trundle-head, so highly geared, as to give a quick motion to the drums, which should be about four feet in diameter. The machine is so con structed, as to manufacture lumber from four to ten feet in length, and front two to ten inches in width, and of any thickness. It has been introduced into most of the New England states, and has given perfect satisfaction. The supe riority of the lumber has, for three years past, been sufficiently proved in this town, (Brunswick Maine,) where there have been annually erected from fifteen to twenty wooden buildings, and for coveting the walls of which this kind has been almost universally used. The principal cause of its superiority to mill sawed lumber, is in the manner in which it is manufactured, viz. in being cut towards the centre of the log, like the radii of a circle ; this leaves the lumber feather-edged in the exact shape hi which it should be, to set close on a build ing, and is the only.wweeyy of the grain in which weather-boards of any kind can be manufactured to witbst red the influence of the weather, without shrinking, swelling, or warping off the building. Staves, and heading also, must be rived the same way of the grain, in order to pass inspection. The mill-sawed lumber, which, I believe, is now universally used in the middle and southern states, and in the West Indies, for covering the walls of wooden buildings, is partly cut in a wrong direction of the grain, which is the cause of its cracking and warping off, and of the early decay of the buildings, by the admission of mois ture. That each is the operation, may be inferred, by examining a stick of timber, which has been exposed to the weather ; the cracks caused by its shrinking all tend towards the heart or centre, which proves that the shrinking is directly the other way of the grain. It follows, that lumber, cut through or across the cracks, would not stand the weather in a sound state, in any degree to be compared with that which is cut in the same direction with them. I have no hesitation in stating that one-half the quantity of lumber manufactured in this way, will cover, and keep tight and sound, the same number of buildings for an hundred years, that is now used and consumed in fifty years. Add to this, the reduction of expense in transportation, and of labour in putting it on, and I think every one must be convinced that the lumber manufactured in this improved way is entitled to the preference.