SAWMILLS. 313 



in order to make the stroke more effective. The log that 

 was being sawn rested on a bench, which was moved for- 

 ward by an automatic arrangment of levers, toothed wheel, 

 and ratchet, so as to bring the log up to the saw at the rate 

 required. Where there is good water-power circular saws can 

 also be driven by water-wheels, though their rate arid strength 

 of cutting is not so effective as steam-driven circular saws. 



The first improvement was to arrange a gang of two or more 

 saws in the frame, these multiple-saws having shorter and 

 thinner blades which work more quickly, but with a shorter 

 stroke, and cause less waste in sawdust. But in any case the 

 stroke of vertical saws is twice the length of the crank, and 

 must be a little over twice the thickness of the thickest part 

 of the log that is to be sawn. 



A further improvement was the muley saw, with its upper 

 end hung in side-slides attached to an overhead beam and 

 the lower ends of the saws attached to a bar directly joined 

 to a pitman, thus doing away with the heavy gate and side-posts 

 of the older saw-frame, and allowing the saws to be slightly 

 inclined forwards so as to give a more effective cutting-stroke 

 in each downward movement. 



Circular saws vary from 2 to 4 ft. in diameter for water- 

 power and small steam-power estate-mills, and up to 6 ft. diameter 

 in large timber-mills. They vary considerably in thickness and 

 in quality, but must be strong to cut through knots, the ordinary 

 thickness being from 12 to 16 gauge (12 being thicker than 16). 

 In large sawmills vertical multiple-saws seldom exceed 14 gauge, 

 and are sometimes only 18 gauge, wasting only -J in. in sawdust. 

 In large mills there may be up to 30 vertical saws in the frame, 

 but single horizontal frame-saws and endless band-saws (horiz- 

 ontal or vertical) are used with a fine gauge (Figs. 88-90). 



Cross-cutting circular saws, for sawing across the grain of 

 wood, are reciprocating and with almost upright teeth, while 

 slitting or ripping saws have their teeth set more at a forward 



