EXPERIMENT IN MINERALOGY. 257 



familiar tokens of crystallisation from a solvent ; they have 

 sometimes rounded edges and sharply defined etched figures, 

 characteristic of an incipient corrosion by the solvent ; an 

 octahedron of alum during crystallisation becomes covered 

 with etched triangles precisely resembling those of the 

 diamond the instant a rise of temperature occurs. 



On the other hand the "blue ground" has the appear- 

 ance of occupying a volcanic vent, and contains fragments 

 of so many other minerals and rocks that it is rash to assert 

 that the diamond may not have been, like them, caught up 

 elsewhere by the molten mass. 



The resemblance between basic terrestrial rocks and 

 meteorites has been frequently pointed out ; there is a 

 regular Gradation from the acid io-neous rocks through 

 the more basic to the felspathic meteorites (which have 

 much the same composition as the basaltic rocks), while 

 lower in the series come the olivine and iron-bearing 

 meteorites, ending with meteoric iron as the extreme 

 limit. 



Now a recent very striking discovery is that of a 

 meteoric iron containing diamond ; the occurrence was 

 announced by Konig (18), and the iron was found in 1891 

 at Canon Diablo in Arizona. Minute particles supposed 

 to be diamond had previously been observed in the meteoric 

 stone which fell at Nowo-urei in Russia in 1886. 



Konig's determination has been subsequently confirmed 

 by the French observers Mallard and Friedel. 



Various forms of carbon had been known to exist in 

 meteoric irons and it had been suggested that some of 

 these were altered diamond, but this substance itself had 

 not been previously found in a meteoric iron. 



It is natural to conclude that the diamond has crystal- 

 lised from solution in the molten metal. 



Moissan has lost no time in putting this idea to a 

 practical test with the help of the high temperature at- 

 tainable by means of the electric furnace (19). He finds 

 that, with the addition of great pressure, he is able to 

 dissolve carbon in iron, silver and certain alloys, and 



that it reappears from the solvent in the form both of 



18 



