Improved Rotary Saw Machine. 151 



The saw may be carried by an eight inch band, when driv- 

 en a proper spee4i (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 straighten the thick edges of the lumber. 



The 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 mo- 

 tion 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 mo- 

 tion, will with great ease penetrate hardened steel, or cut 

 off a file, when applied to its circumference ; and the same 

 principle is applicable to a rotary saw for cutting wood. 

 The requisite degree of velocity is obtained by the con- 

 tinuous 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 

 required to sharpen them. If the velocity of the saw were 

 slackened to a speed of but 40 or 50 times per minute, it 

 would require at least four such bands to carry it through 

 a log as above described. 



One machine will cut from 18 to 20 hundred square feet 

 of pine timber per day, and two of them may be driven by 

 a common tub wheel 7 or 8 feet in diameter, having 6 or 7 

 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 

 constructed, as to manufacture lumber from 4 to 10 feet in 

 length, and from two to ten inches in width, and of any re- 

 quired thickness. 



It has been introduced into most of the New England 

 states, snd has given perfect satisfaction. The superiority 

 of the lumber has for three years past been sufficiently pro- 

 ved in this town (Brunswick, Me.) where there have been an- 

 nually erected from fifteen to twenty wooden buildings, and 

 for covering 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 manufac- 

 tured, viz,; in being cut towards the the centre of the log, 

 like the radii of a circla ; this leaves the lumber feather 



