88 H. J. Grayson: 



this characteristic note. The writer's experience, extending over some 

 20 years, of the behaviour of a diamond during the act of ruling is 

 that its action should be practically free from any appreciable 

 sound or note of any sort. Anything approaching a distinct hissing 

 or singing note has invariably l>een regarded as evidence that the 

 lines thus being ruled would show, when examined miscroscopically, 

 some indication of a vibratory or chattering effect upon the surface 

 ruled, and that the " life " of a diamond operated under these 

 conditions would be comparatively short. Apart from this some- 

 what contradictory position with respect to the experience of others 

 whose work has extended over a considerable period, the article 

 referred to contains much interesting information. 



One other reference to the action of a diamond when ruling 

 appears in the collected Researches of tlie National Physical Labora- 

 tory, Vol. VIII., 1912. The results therein embodied have pre- 

 sumably been derived from experience in ruling with the Blythes- 

 wood Engine. So far as the method of using a diamond is there 

 explained, the writer is in full agreement; with certain other 

 statements and procedure there recorded his experience is at 

 variance. 



With respect to the choice and selection of diamonds suitable for 

 ruling. After an experience extending over 20 years the writer 

 prefers diamonds found in the diamondiferous drifts of New South 

 Wales. These stones are both harder and tougher than any other he 

 has hitherto obtained. Both Cape and Brazilian stones have been 

 tried; also the so-called black diamond, carbonado and " bort," 

 nearly all the varieties of which are more or less crypto-crystalline 

 and unsuited for ruling except for the coarsest lines. The best 

 Australian stones for ruling work are those showing smooth, bright 

 crystalline faces, the simpler octahedral forms affording the best 

 results. The more complicated the crystalline structure, the fewer 

 the splinters adapted for ruling obtainable from a given gem. 

 Cleavage fragments intersecting the smooth outer surface of a 

 stone frequently give excellent results and are very durable. 



For breaking the stones, a small mineralogical hammer and hard 

 steel anvil are required, with provision to prevent loss of flying 

 fragments. Straight smashing blows must be avoided^ or the stone 

 will be reduced to dust. A dragging blow ranging from a sharp 

 tap to one of considerable force may be used ; changing the position 

 of the stone until success is attained. 20/- worth of selected stones 

 will serve for a lifetime if properly vised. Once a stone has been 



