MODE OF USING SAWS. 189 



as it is more economical of the wood, and, after a little 

 experience, is more labour-saving than the latter method. 



iii. Machine -sates. 



Attempts have often been made to fell trees by machine- 

 saws, driven by steam or hand-power. Eansome's steam-saw, 

 manufactured by A. Koppel, Berlin, as shown in Fig. 109, 

 is the best known in Germany. Hitherto the use of these 



saws has not proved effective in European forests. In 

 North America, where trees are either felled in the open, or 

 wholesale in forests, without any care for the undergrowth, 

 they may be serviceable : but chiefly the axe is used in the 

 extensive Pacific Coast and mountain forests. 



(d) Mode of Using Forest Saws. 



This depends on the material of which the saw is composed, 

 its shape, dimensions, curvature, weight, shape of teeth, 

 amount of set or extent to which the teeth are bent to either 

 side of the plane of the blade, their degree of sharpness, and, 

 finally, on the kind of wood to be cut and the use to be made 

 of the wood. The strength of the workman and his degree of 

 skill in using saws are also important factors in the question, 

 although it is difficult to estimate them. 



The material of which the saw is made is so far important, as 

 it determines its temper and how long it will remain sufficiently 

 sharp and retain its set. Saws rolled out of cast steel are best 

 in these respects. 



As regards shape, curved saws are preferable to straight 

 ones, especially for coniferous wood, and a radius of 6 feet 



