TOOLS 



169 



the other concaved. In most of the razors of American make 

 the steel is too hard and brittle, as a consequence the edges 

 chip, necessitating frequent grinding and honing. It is there- 

 fore advisable to try and obtain 

 a section razor whose steel is 

 hard enough to hold a fairly 

 keen edge, but not so hard that 

 fragments are chipped out by 

 any hard particles which may 

 be encountered in the material 

 being cut. The edge should 

 turn, not chip. Small pieces of 

 soft material to be roughly sec- 

 tioned may conveniently be held 

 between pieces of elder pith and 

 clamped in the jaws of the 

 microtome ; a few drops of alco- 

 hol applied to the pith causes it 

 to swell and to hold the specimen tightly in place. Imbedding 

 in paraffin or celloidin is of course much better. 1 



Tools, etc. A Jeweler's hack saw with wide and narrow 

 blades (Fig. 107) will be required to cut off bits of metal and 



FIG. 106. Small " Table " Microtome. 

 Spencer Lens Co. 



FIG. 107. Jeweler's Hack Saw. Sections of blades are shown full size. 



alloys, to cut through specimens to study the thickness of coat- 

 ings, platings or enamels (most enamels cannot be cut with a 

 hack saw); to cut through primers, fuses, etc., in the study of 

 ammunition, etc., etc. These tiny hack saw blades are very 



x The student will find in Gage: The Microscope, i3th Ed. 1920 (Comstock 

 Pub. Co., Ithaca, N. Y.), detailed directions for imbedding methods. 



