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feet per second, while others, of equally good authority, say 

 one hundred feet and more per second. The diaj^Mr of the 

 saw has much to do in this respect. A circular sa^Mwenty-lwo 

 inches in diameter, has a cutting edge of sixty-nine Aches. Now, 

 if it revolves twelve hundred times in one mi; nttmrr 



edge will move one hundred and fifteen feet per second, or fix thou 

 sand nine hundred feet per minute ; and if the wood to be sawed 

 be as large as that saw will cut in two without turning it over, 

 by putting another saw of the same thickness, having teeth the 

 same distance apart, which is twenty-six inches in diameter on 

 the same mandrel, the same amount of power will saw more than 

 it will with the saw twenty-two inches in diameter. It will require 

 a little more power to drive the twenty-six-inch saw, because it 

 is a little heavier ; but the difference is so small that it cannot be 

 perceived. And the diameter of the saw being greater, there 

 will be a greater leverage to absorb the driviug power. But the 

 velocity of the cutting edge of the twenty-six-inch saw being (at 

 1200 revolutions per minute) one hundred and thirty-six feet per 

 second, together with the greater diameter of the saw, by reason 

 of which, in sawing materials of the size already mentioned, 

 fewer teeth cut at the same time, both operate in favor of the 

 large saw. Consequently, a twenty-six-inch saw will do more 

 with the same power than a twenty-two-inch saw, in sawing 

 wood that is nearly all as large as a twenty-two-inch saw will 

 reach through ; the teeth and thickness of the plate being the 

 same. If, now, the speed pulley on the saw mandrel be made 

 so large as to give the cutting edge of the twenty-six-inch saw 

 a velocity of one hundred and fifteen feet per second, the same 

 amount of power will saw more than when the velocity of the 

 teeth was one hundred and thirty-six feet per second. If the 

 tyro should have much sawing to do, and his power limited, it 

 would be well worth while to have two or three different speed 

 pulleys to put on the saw mandrel. The size of the pulleys 

 would very soon decide whether too much of the power was 

 absorbed in producing a higher velocity than will be most effect 

 ive for the amount of power employed. The driving wheel may 



