Wolff — Apparatus for the Geological Laboratory. 355 



eastward. Localities on the western border have a steep west- 

 erly dip in many instances ; in others the border series as a 

 whole is nearly in a vertical position. Many areas occur along 

 this belt where the series is overturned to the west, but the 

 exact angle at which the strata lie is difficult of determination. 

 The orographic thrust producing the folding was directed nearly 

 from the east and west. Normal faults and overthrusts are 

 indicated but data for their detection is not now at hand except 

 in one instance. 



Cambridge, Mass., January 10, 1894. 



Art. XXXVIII. — Notes on Apparatus for the Geological 

 Laboratory • by J. E. Wolff. 



The utility of the following methods and apparatus having 

 been established by laboratory practice a brief description of 

 them may be of benefit to others, a familiarity with the usual 

 methods being assumed. 



Diamond /Saws. 



These are made in the laboratory as follows : Disks of ordi- 

 nary sheet tin are procured from a tinsmith, 6 inches in diam- 

 eter, with a central hole |- inch in diameter to fit the arbor of 

 the lathe. Two round wooden blocks are turned out from 

 board, about 5|- inches in diameter, and a central hole of the 

 same size as that of the disk bored in one, while a correspond- 

 ing round wooden stick is set into the center of the other. 

 The tin disk is then placed between the two blocks, the round 

 stick holding it central, and the whole fastened in a vise. The 

 edge of the disk projecting beyond the wood is then notched 

 by a shoemaker's knife which is held against it and struck a 

 sharp blow with a light stick, but the plane of the knife is 

 held slanting or oblique to the plane of the disk and not trans- 

 verse, and moreover is inclined on opposite sides in adjacent 

 quadrants. The notches are made as close together as possible 

 without breaking the tin and about T X T inch deep. The bort 

 (preferably the so-called scrap carbon left as waste from dia- 

 mond drills) is pulverized in a diamond mortar to a fine sand, 

 corresponding nearly to grade 100 in corundum or emery 

 powder, mixed with a little oil to form a stiff paste and inserted 

 between the teeth of the saw by a pointed match. The edge 

 is then gently hammered back to a plane, using a light ham- 

 mer on an anvil, and the saw then turned over and hammered 

 smooth on the other side. It requires one carat of bort to 



Am. Jour. Sol— Third Series, Vol. XLVII, No. 281.— May, 1894. 

 24 



