1 873.] New Facts concerning the Diamond. 447 



change of the state of aggregation, bubbling up, melting or 

 softening, rounding of corners and angles, were in no case 

 presented to our notice. Once only in experimenting upon 

 an opaque greyish diamond, a few sparks were emitted, but 

 these were evidently due to the presence of some foreign 

 elements incorporated with the whole. Neither did the 

 diamonds burst or split, save in one case, where such was 

 foreseen by M. Daniels: a stone, evidently composed of two 

 diamonds joined together, upon the first application of heat 

 broke with considerable violence into two fragments, each 

 constituting a decided crystal. 



It has been asked if the combustion of the diamond in 

 oxygen or atmospheric air is accompanied by flame. M. G. 

 Rose denies this completely, but his mode of operation, 

 namely, by heating the diamond upon a cupel in the muffle 

 of a reverberatory furnace, and drawing it out from time to 

 time for examination, or by heating a thin piece of diamond 

 upon platinum foil in the flame of a blowpipe, was not 

 well calculated to settle the question. On the contrary, by 

 the above method, all that took place in the crucible could 

 be distinctly seen through the sheet of mica, and thus ample 

 evidence was obtained that the diamond, while in a state of 

 combustion is surrounded by a small flame, the exterior 

 envelope of which is a violet-blue, similar to that produced 

 by oxide of carbon in a state of combustion. This is 

 especially the case when the diamond is rather large, when 

 the lamp has been withdrawn and the platinum has ceased 

 to glow : the diamond is then seen upon the black ground 

 of the crucible, brilliant with vivid white light, and sur- 

 rounded by a zone or aureole somewhat less bright, its 

 exterior edge being a blue-violet colour. 



Some highly interesting microscopic observations relative 

 to the dull surface of diamonds which have undergone 

 partial combustion have been communicated by M. G. Rose; 

 he has discovered on them regular triangular markings 

 that resemble those occurring in abundance on the fine 

 crystals from the Vaal River, and recall the faces formed 

 on planes of crystals, soluble in acid, by the slow and im- 

 perfect etching action of such a reagent ; as, for example, 

 the action of hydrogen chloride on calcite. Like them, 

 these depressions on the diamond bear an exact relation to 

 the crystalline form, and are determined by certain definite 

 faces, their sides being parallel to the edges of the octahedral 

 faces of the crystal. Measurement with the goniometer 

 shows them to belong to the icositetrahedron, the faces of 

 which have not been met with on diamond. These 



