718 



SEC. 16. GEOLOGY AND MINING. 



The machine consists of a mahogany, oak, or beech framework (a a), 

 similar to that of an ordinary turning lathe, and is supplied with crank, fly- 

 wheel, and treadle, occupying a floor space of 2 ft. 2 in. by 20 in. To the 

 bed of this frame is fitted an iron casting (B), bored to receive two spindles, 

 viz. : a vertical spindle (D), which carries the slitting disc, grinding laps, &c., 

 and another spindle (E), to which is fixed a horizontal plate (F), carrying 

 on its surface a cup containing cement, in which the material to be cut is 

 imbedded, and which is retained and uniformly pressed against the slitting 

 disc by means of a cord attached to the plate, which, passing over a pulley 

 having a suspended weight (G), gives a constant and regular pressure to the 

 plate containing the specimen. There is also a convenient screw arrangement 

 by which this plate can be accurately adjusted for the purpose of regulating 

 the thickness of the slice. The slitting disc and laps are made to revolve, at 

 the rate of about 500 revolutions per minute,, by means of a treadle used in 

 the ordinary way. 



3329. Apparatus for the preparation of rock sections, and 

 plates of crystals for examination in polarised light. 



R. Fuess, Berlin. 



3330. Apparatus for the preparation of Thin Microscopic 



Sections of rocks and minerals : 



1. Cutting apparatus. 



2. Grinding and polishing apparatus. 



Christ. Weber, Eisenach. 



3331. Portions of the Geological Special Map of 

 Prussia, and the Thuringian States. 



The district of ILFELD, HARTZ ; 6 sections. 

 The district of the OHM MOUNTAIN ; 6 sections. 



