24 



this platform are two screws fixed in position at one end, and at 

 the other is a movable toothed bar, which slides up and down in 

 a slit, by which means the rock to be cut may be held firmly 

 between three supports. There is also a square box, provided 

 with wax, to which to fix smaller specimens. These movable 

 parts have beneath them a zinc tray, perforated where necessary. 

 There is no arrangement for polishing the sections. 



68. Apparatus for cutting and grinding rocks and 

 fossils for microscopical examination. 



E. 49. 1885. Made by E. Fuess, Berlin. 



This is adapted for cutting sections of a not greater diameter 

 than 1^ inches. It has the same form as No. 67, but on a 

 smaller scale. The arrangements for rotating the vertical slitting 

 disc are identical, but the tin covering is more open, the specimen 

 to be cut being brought to the slicer from the side and not from 

 below. The rock holder as before is on a lever worked in the same 

 way by two forked weights moving on the longer arm, but instead 

 of being a platform it consists of a vertical bar movable and clamp- 

 able in its own direction. At the end it carries a second bar, 

 movable through it in a horizontal direction, and this carries a 

 third bar movable through it in another horizontal direction at 

 right angles, to the end of which is fixed a circular disc, 1 \ in. in 

 diameter, to which the rock specimen is cemented. These arrange- 

 ments allow of the placing of the specimen in any desired posi- 

 tion in relation to the slitting disc. But as in all positions the 

 face of the supporting disc is parallel to the surface of the slitting 

 disc, the specimen must be orientated with the surface of the 

 support in the process of cementation. There are additional cut- 

 ting discs of various diameters. The grinding portion of the 

 apparatus consists first of a pair of wheels fixed obliquely on the 

 under side of the horizontal framework, by passing the cord 

 round which the vertical is converted into a horizontal rotation, 

 which revolves a polishing lap, protected by a zinc tray. An extra 

 lap is provided with the machine. 



69. Machine for cutting slices of rocks and fossils, to 

 work by hand. 



E. 40. 1884. Made by E. Fuess, Berlin. 



This stands on an 8 in. square wood block ; the motion is pro- 

 duced by turning a vertical cogwheel by the projecting handle. 

 This cogwheel is about 10 in. in diameter, and works into another 

 about 1J in. diameter. To the latter is fixed a vertical slicing disc 

 with a tin protector. The specimen is held in its place by the 

 same leverage arrangement and sliding bars as in No. 68, but 

 the whole is on a smaller scale. There is no arrangement for 

 polishing. 



