PEACTICAL FORESTRY. 



27 



poles cut in the woods instead of over metal rails; often they are 

 rolled into slides built of other logs, and either move downhill by their 

 own weight or are dragged along by horses, cattle, or steam. In 

 southern swamps the logs are sometimes swung up by a wire rope sus- 

 pended from the trees, and so are loaded on the great flatboat which 

 carries them to the mUl. 



At the mills. — At the mills the logs are cut into lumber by various 

 kinds of saws. Of these the circular saw is still very widely used, 

 although the wide bite or kerf which it cuts in the log makes it very 

 wasteful of timber. A large circular saw makes a kerf a quarter of an 

 inch wide, so that in cutting four one-inch boards enough wood to 



Fig. 17. — Eiver drivers at work on a log jam. Minnesota. 



make a fifth board is ripped into sawdust. Band saws are far less 

 wasteful, for they are thinner and make a narrower kerf. Hence they 

 are taking the place of the circular saws, although they do not work so 

 rapidly. Many mills, in addition to their band saws or circulars, use 

 gang saws, which cut out several boards at the same time. 



Besides lumber, the best sawmills produce great quantities of lath 

 and shingles, made either from small logs called "bolts," cut specially 

 for that purpose, or from slabs, edgings, and other pieces of wood 

 which might otherwise be wasted. But in spite of every effort to pre- 

 vent waste in the mill by using sawdust and other refuse for fuel, and 

 in other ways, very many thousands of tons of wood a year are 

 thrown into great burners as the cheapest method of getting it out of 

 the way. 



358 



