Accessory Apparatus 257 



an old well-used strop is simply invaluable. Always keep 

 the strop hanging up in one place as free as possible from 

 dirt and damp. It is well after honing to thoroughly dry 

 both knife and blade-holder ; then, having the blade-holder 

 adjusted upon the knife, the stropping is done as follows : 

 Lay the point of the knife upon the right-hand side of the 

 strop, concave side downwards, and push the knife across 

 the strop from point to heel and from right to left upon 

 the strop, back forwards, making the point of the knife 

 inscribe an arc. Maintain a similar process upon the 

 opposite side of the knife, remembering what is above 

 mentioned respecting the grain of the strop. Never grind 

 a knife more on the plane side than upon the concave, 

 rather the less upon the plane side. During the stropping 

 it will be found convenient to sit upon a low chair, and 

 while holding the strop to allow it to rest upon the knees 

 as well. The stropping must not be done by alternate 

 strokes, to first one and then the opposite side of the 

 knife, but by a succession of strokes upon one side of the 

 knife. 



Testing the Knife Edge. — When finished, the edge of 

 the knife under a power of 100 diameters should present a 

 perfectly straight and even edge, whilst with 250 diameters 

 there should be a suggestion of faint serrations. These 

 small serrations will prevent the crushing together of the 

 paraffin sections as they are cut. Before examining the 

 knife under the microscope, allow a drop of benzole or the 

 like to run along the edge; then wipe with a clean soft 

 leather, otherwise the slight amount of grease from the strop 

 will obliterate the fine serrations; even an objectionable 

 notch may be hidden in this manner, giving a false concep- 

 tion as to the real state of the edge. A fair knife-edge should 

 cut a ribbon of sections 10 /« thick from a paraffin block 

 having a surface 1 centimetre square without any perceptible 

 crushing together. It will be excellent practice for a beginner 

 to go through with this experiment until satisfaction is 

 attained. It will perhaps take a little time, but the practical 



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