j 7 6 THE POPULAR SCIENCE MONTHLY, 



surface, or as to the direction of travel, or as to the correction of cross 

 or longitudinal irregularities of surface. 



The guide as to depth of cut is that which probably first pre- 

 sented itself as an important appendage to a chisel, and it has led to 

 a form of tool of a very useful construction, although of limited range. 

 The instrument is called a " spoke-shave." In this case the tool is 

 that in Fig. 5 with the guide principle introduced, the depth of cut 

 being determined by the nearness of the edge to a parallel wooden 

 handle. 



This tool, owing to the position of the application of the power, 

 viz., the hands, and the tendency of resistance by the work to turn 

 the whole tool in the hand, is not of general use ; where, however, the 

 curvature of surface varies, the parings to be removed are light, and 

 the workman can have convenient access, the tool is one capable of 

 doing good work, and, in some respects, possesses advantages over 

 the plane, to which it probably formed an introduction. 



The plane, in its most simple form, consists of a chisel inserted at 

 an angle into a box, generally of wood, and with the cutting edge of 

 the chisel projecting through the bottom of the box. If the actions 

 of a workman be noted as he is smoothing wood with a chisel alone, 

 it will be seen that he holds the bevel edge on the wood, and so 

 elevates or lowers the handle as to secure a proper and efficient cut. 

 Then he advances the tool in a line at right angles to its cross-sec- 

 tion. If, now, instead of thus continuing to hold the tool, the chisel 

 was so fixed in a movable piece of wood as to be at the same angle 

 as the workman required, then, if the mouth were broad enough, and 

 the instrument were propelled along the wood, a shaving would be re- 

 moved very nearly the same as that obtained from the chisel alone. 



In the arrangement thus sketched the workman would be relieved 

 from the care needed to keep the tool at a constant angle with the 

 surface of the timber. There is, however, a fixity of tool here, and 

 consequently an optional or needful adjustment called for by any 

 varying condition of the problem cannot be had. When operated 

 upon by hand alone, if an obstacle to the progress of the tool is pre- 

 sented, as, for instance, a twist or curl in the fibre or grain of the 

 plank the presence of a knot then the workman by hand can adjust 

 the handle, and so vary the inclination of the cutting edge as the cir- 

 cumstances of the case require. Not so if the tool is securely fixed 

 in a box as described. 



While, therefore, one gain has been had, one loss has been encoun- 

 tered. Can the gain be made to more than counterbalance the loss? 

 This can only be answered by observing the defects of the primitive 

 plane, as hitherto described, and noting what hopeful elements it 

 contains. 



The front of the sole of the box will clearly prevent the pene- 

 tration of the incased chisel into the wood, because it cannot now be 



