﻿48 INTRODUCTORY. 



As yet no experiments with tubular bort-charged drills have been made ; but 

 such revolved at a steady, even rate should yield even better results than the plain 

 drill-edge and loose bits of chilled steel employed as above described. Whatever 

 the plan used, or whatever the part of the cutting process that is being carried out, 

 heavy thrusts, strains, or jars are to be avoided. It is quite interesting in this con- 

 nection to recall that the Swiss lake-dwellers bored limestone with reeds having a 

 large pith, by first pushing out this pith and then revolving the tube thus obtained 

 in loose sand filled in about the cutting end, by means of a whirling-bow like that 

 used in primitive fire-making. As shown by experiment, this apparatus cuts with 

 fair rapidity. Cores nearly an inch in diameter and pieces of stone worked on by 

 the lake-dwellers are in the museum at Zurich. 



In closing the present brief description of methods it may be added that the 

 difficulty of cutting sections and mounting them of course increases with their size. 

 It is the writer's belief, however, that given time for the devising of simple appliances, 

 it would be possible to cut thin sections from large entire trunks. To complete the 

 polishing of the large sections made by the writer a fine carborundum whetstone 

 was sometimes used. By this means dark portions may be thinned, so as to let the 

 desired amount of light through without thinning out the more transparent portions 

 too much, or losing thin, weak, or crumbling edges or parts of the section. This 

 device will prove of occasional service ; for it is not always possible to secure the 

 best results by grinding or polishing all of the surface of a large section equally. 

 By so doing the natural color effects are often partly lost, or even valuable parts of 

 the section itself, long before all of the section is sufficiently thin. It was also 

 found that instead of renewing the Canada balsam, as it wears away and exposes the 

 edge of the section near the close of the polishing process, it is rather better to 

 dissolve away with benzol the balsam from all around the section. This prevents 

 relatively coarser particles of carborundum from rolling up over the balsam and 

 shattering and cutting off the section borders, especially when the sections are of 

 large area. All the larger sections are mounted on specially cut and ground plate 

 glass of suitable thickness, and selected with reference to its hardness, toughness, 

 and transparency. 



