PEOCEEDINGS OF THE SOCIETY. 575 



meter. In Mr. Fletcher's opinion, the two " points " were untouched 

 by the mill ; diamond No. 4 consisted of two cleavage faces meeting 

 in the edge, and was untouched by the mill ; in all the other cases 

 one of the faces meeting in the edge was an untouched cleavage face • 

 the other had been polished, and in some cases an additional facet 

 or two developed on that side ; the alteration of the cleavage-angle 

 he regarded merely as an incident of the polishing. En resume, there 

 were seven diamonds, each having two principal faces meeting in an 

 edge, one face in every case being an untouched (unpolished) cleavaf^e 

 face, whilst the other was polished ; one diamond had two cleavage 

 faces meeting in an edge, and both faces were untouched (unpolished) ; 

 the remaining two were "points," not touched by the mill. The 

 goniometer showed that in the polishing the angles had been altered 

 from the natural cleavage planes by quantities varying from a few 

 minutes up to about 6°, and, as no two were exactly alike, it might be 

 assumed that, as Mr. Fletcher suggested, " the alteration of the angle 

 is merely an incident of the polishing," and not a condition distinctly 

 aimed at by Herr Nobert. 



In the face of Mr. Fletcher's opinion, Mr. Mayall said that he 

 must withdraw the statement he had made at the previous meeting 

 that some of the diamonds appeared to have two polished surfaces 

 meeting in one edge. On closer examination in Mr. Fletcher's 

 presence, he found that certain striations on the surfaces, which he 

 had regarded as imperfectly polished, were more probably untouched, 

 and therefore he now gave his adhesion unreservedly to Mr. Fletcher's 

 judgment. 



Regarding the mode of preparing the ruling diamonds adopted by 

 Herr Nobert, Mr. Mayall said he had no record save the diamonds 

 themselves. The matter could only be decided by conjecture. After 

 various consultations with diamond experts, he had come to the con- 

 clusion that diamonds, exhibiting under the Microscope precisely the 

 character of the seven " edges " to which he had referred, could be 

 prepared from the fragments of gem diamonds met with at any dia- 

 mond cleaver's. The cleaver would select a fragment which would 

 admit of two faces being cleaved to an edge of about 1/16 in. or 

 1/20 in. in length ; one of these faces should be perfectly polished on 

 the mill as near as might be parallel with the cleavage face ; the 

 other face should then be cleaved again parallel to its former cleavage, 

 so as to remove the edge, which would probably have been somewhat 

 rounded by the mill, thus furnishing a new and probably sharper 

 edge— a clean fractured surface meeting the flat polished surface ; the 

 diamond should then be mounted in a soft metal in a notch at the 

 end of a piece of brass wire by means of a blowpipe. Such fragments 

 of diamonds had but little commercial value. A diamond cleaver in 

 Antwerp had estimated the cost of supplying them complete at less 

 than ten shillings each. After referring to the various notes on the 

 diamonds coijktained in Herr Nobert's memorandum-book, Mr. Mayall 

 said he had no doubt the publication of the data obtained from the 

 examinations of the diamonds would further the interests of micro- 

 metry. Several ruling machines existed both in Europe and America 



