SAWMILLS. 495 



mechanism to replace manual labour in working the mills. As 

 the question there is one of entirely clearing the forests of 

 wood, for which purpose tramways are constructed expressly 

 and penetrate every year deeper into the forests, it is evidently 

 business-like to set up pony-saws in the midst of the forest ; 

 nowhere therefore are various kinds of pony-saws more the 

 order of the day than in California. They work generally 

 with circular saws. 



2. Circular Sirs. 



Circular SHAYS consist of a circular thin steel blade furnished 

 at its rim with a continuous row of teeth and capable of rapid 

 rotation round a horizontal axis. These saws are vertical, and 

 only about 5 of their area is available for work. 



Circular saws require a comparatively low motive power; 

 their dimensions vary considerably from 8 in. to 4 feet (0'20 to 

 l'20m.) diameter, whilst the thickness of the blade varies from 

 1 to 3*5 mm. A moderate-sized circular saw moves, at its 

 circumference, at the rate of 50 to 65 feet (15 to 20 m.) a second, 

 for hardwood and (>5 to 100 feet (15 to 30 mm.) for softwood. 



The commonest uses of circular saws are as follows : 



i. Large circular saws for removing side-pieces from beams, 

 thus replacing much tedious work with the adze. Although 

 this can be done also by frame-saws, yet the circular saw is 

 often preferred, as it works the more quickly of the two. By 

 means of mechanism, the log resting on rollers moves automa- 

 tically towards the saw. 



ii. Large saws for cutting butts into planking; these are 

 generally used after the butts have been sawn in half by 

 frame-saws. Circular saws are used much more commonly 

 for this purpose in America than in Europe. 



[Where driven by engines of from 25 to 100 horse-power, 

 the circular sawmill will turn out 20,000 to 60,000 feet a day 

 in addition to running double-edge and trimming saws, trim- 

 ming off the rough edges and bad ends of the lumber.* Tr.] 



iii. Double-edging circular saws for edging planks and boards 

 consist of two saws on the same axis, the distance between 

 them being capable of adjustment. They feed by rollers. 



* " Encyc. Brit.,'' USSii, vol. xxi., p. :<45. 



