226 Notices of Memoirs — Artificial Diamonds. 



series, and cannot be divided by an unconformity. That this assump- 

 tion is unwarranted has again and again been proved. The break 

 at the base of the Llandovery alluded to by our authors is, both in 

 Shropshire and at Llandovery, between rocks of very similar 

 character; and such is the case, it is generally stated, between the 

 upper and lower parts of the Old Red Sandstone in Herefordshire, 

 and between the Elgin and the Old Eed Sandstone in Scotland. In 

 most of these cases the separation is effected by the aid of the fossils, 

 but in the present case stratigraphy has to do the work alone, and it 

 is perfectly capable of doing it. 



I trust that in the above remarks I may in no case have made 

 a statement without at the same time indicating plainly how it may 

 be checked, nor quoted my own opinion without giving any reasons 

 for it, both of which procedures I hold to be inconsistent with 

 scientific arsrument. 



n^OTiOES OIF DvcEnvLoii^s- 



I. — Herstellung von Diamanten in Silikaten, entsprechend 



DEM NATIJRLICHEN VoRKOMMEN IN KaPLANDE. Vortrag gchaiteU 



im Verein zur Beforderung des Gewerbfleisses am 7 Februar, 

 1898, von L Friedlander. (Berlin, 1898.) 



(Artificial Production of Diamond in Silicates, corresponding 

 TO the Actual Mode op Occurrence in South Africa.) 



IN the recent diamond-making experiments of M. Moissan, fused 

 iron rich in carbon was allowed to cool in such a way that the 

 separation of the excess of carbon took place under pressure, and it 

 was thought that a high pressure was necessary to the success which 

 had been attained. It is now known that the necessary pressure is 

 not very high, for microscopic diamonds have been found as normal 

 constituents of ordinary cast iron. In South Africa no iron is present 

 in the metallic state in the diamond-bearing rock, although it is 

 largely present as a chemical constituent of the stony matter. Hence, 

 in regarding Moissan's method as being possibly identical with the 

 one by which the South African diamonds had been formed, it was 

 necessary to surmise that the ciystals, after formation in the molten 

 iron at some great depth below the earth's surface, bad floated into 

 the molten silicate-material above. It was, however, soon pointed 

 out that the diamond-bearing rock, if in a state of fusion at small 

 pressure, dissolves any diamonds contained in it. 



Dr. Friedlander fused a small piece of olivine, a centimetre in 

 diameter, by means of a gas-blowpipe, kept the upper portion in the 

 molten state for some time by playing upon it with the flame, and 

 stirred it with a little rod of graphite. After solidification the silicate 

 was found to contain a vast number of microscopic crystals, but 

 only in the part which had been in contact with the carbon. These . 

 Dr. Friedlander has subjected to a careful examination. They are 

 octahedral or tetrahedrai in form, are unattached by hydrofluoric 

 and sulphuric acids, have a high refractive index, sink slowly in , 



