688 SAW-MILLS 



mode of construction, they are on wheels and are driven by a 

 belt from a locomobile ; they are valuable in forestry from the 

 fact that it is more natural to transport saws to the forest, than 

 wood in bulk from the forest to the saw-mills. 



California is at present ahead of all other countries in saw- 

 mills, not only in constructive ingenuity, but also in the use of 

 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 expressly constructed 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 generally work with circular saws. 



2. Circular Sans. 



Circular saws 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 > 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 — 

 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 — 65 feet (15 — 20m.) a second, 

 for hardwood and 65 — 100 feet (15 — 30m.) 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 also be done by frame-saws, yet the circular saw is 

 often preferred, as it works the more quickly of the two. l^y 

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

 cally 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 much more commonly used for this 

 purpose in America than in Europe. 



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

 rirculur saw-mill will turn out 20,000 to 60,000 feet a day in addition 



