80 H. J. Grayson: 



Plate XV. 



New Rock-Slicing Machine, Melbourne University. Top 

 view or photograph in plan serving to show the machine in work- 

 ing order. To the right of the view the slicer and one clamp are 

 seen in position for slicing. A. second clamp, for holding 

 massive rocks, is shown on the extreme right ; while the gonio- 

 meter as adjusted for the slicer is seen in the right front corner 

 of the guard tray. The two grinding laps, with supports and 

 clamp adjustments for specimens, follow in order to the left of 

 the slicer. Ordinarily, in the preparation of rock sections, the 

 clamps above the grinding laps are not required ; but in all 

 operations involving pi'ecision their use is indispensable. The 

 emery wheel and polisher referred to in the paper are situated on 

 the extreme left of the table. A graduated 60 inch scale, the 

 divisions on which are unfortunately not reproduced, lies along 

 the front of the guard trays. 



Plate XVT. 



New Rock-81icing Machine, Melbourne University. Driving 

 mechanism in detail. The usual fast and loose pulley driven by 

 tlie motor are seen upon the main shaft on the left of the photo- 

 graph. To the right of these, the shaft passes successively 

 through each driving pulley, which, in turn, connects with the 

 machine below by means of a leather band. The pulleys, ordin- 

 arily stationary with the shaft running through them, are 

 brought into action by the lever which forces the cone on the left 

 under the lever of the clutch attached to the hub of each pulley. 



Platk XVII. 



New Rock Slicing Machine, Melbourne University. Fig. 1, 

 Arrangement for serial section cutting. Fig. 2, Gonimeter 

 attacliment in position for grinding facets, etc. In Fig. 1, in 

 addition to the usual clamp, which swings radially over the 

 grinding lap, a graduated disc is shown. This disc is keyed to 



