70 H. J. Grayson : 



describe it with siitticient detail to enable others to benefit 

 by uiy experience. As the method of rock slicing and section 

 mounting are, in a measure, related and co-ordinated, it is 

 necessary also to include a short account of the latter process. 



2. — Structural Features of the New Machine. 



A detailed description of all the working parts of the 

 machine, with plans to scale, is beyond the scope of this paper. 

 Fortunately they are not, I think, necessai'y, as with the aid of 

 photographs (Plates XIV. to XVII.) showing all the essential 

 features of the apparatus and descriptions of less obvious 

 features, it should be possilile for an intelligent mechanic to 

 construct a similar machine. 



At the outs*t it is necessary to point out that in the build- 

 ing of the apparatus. I was strictly limited as to position and 

 space. 



Dealing with the several portions of the machine in order: 

 — Plate XIV., which may be regarded as equivalent to a sec- 

 tional or front view, shows all the principal features of the 

 apparatus, which is l)uilt into a corner of the workroom ; the 

 lathe in the foreground has no connection with the rock slicer, 

 beyond being driven by the same motor. The three guard 

 trays have been removed from the top of the rock machine 

 table, in order to show the position and relation of the slicing 

 and grinding-lap spindles, and of the several supports for rock 

 holders and clamps. 



Plate XV. may be regarded as a photograph in ]ilan — i.e., 

 looking down upon the machine. It shows to better advantage 

 the relation of the working parts in running order, other than 

 the driving mechanism, which is situated at some height above 

 the machine, and is shown in detail in Plate X^ I. 



Plate XVII. (Figs. 1 and 2) serves to show the special appli- 

 ances for serial section cutttng, parallel grinding, and work with 

 the goniometer. 



Reverting to Plate XIV., it will be seen that the base of the 

 machine is a strongly built wooden bench or table with dimen- 

 sions as follows: — Length, 7 feet: width, 2 feet 4 inches; 



