iSogal imtitution ot ffireat iSritain, 



WEEKLY EVENING MEETING, 



Friday, March 23, 1860. 



The Lokd Wensletdale, Vice-President, in the Chair. 



NEViLii Stoey Masblelyne, Esq. 

 On Diamonds, 



The progress of chemical discovery in so fundamental and important 

 a subject as the elements, has been hitherto singularly incommensurate 

 with the rapid strides of theory and the vast accumulation of facts 

 regarding the compounds, which those elements combine to form. Of 

 this, the element carbon is a remarkable illustration. 



Organic chemistry is the chemistry of carbon, yet even now the 

 number of alio tropic states of that element are undetermined with any 

 certainty. Evefe the question of the crystalline system of graphite is 

 not decided ; and, while [we are almost entirely ignorant of the real 

 conditions requisite for the production of carbon in any of its allotro- 

 pic states, we are completely in the dark about those under which the 

 diamond, and the strange mineral kindred to it called *' carbonate " 

 have been, or may be called into existence. 



The transcendant hardness of the diamond is a quality which 

 would alone make so rare a body very costly, even if it had no value 

 as a gem. [The apparatus employed by the diamond-cutter for cutting 

 the diamond by means of its own dust was exhibited ; consisting of 

 the schyf or horizontal iron wheel armed with this dust, on which 

 the diamond is pressed by weights, laid on an arm of wood, below the 

 end of which arm. the diamond is carried in a projecting bed of 

 fusible metal.] 



Another remarkable characteristic of the diamond is its adamantine 

 lustre, arising from the reflection of so large an amount of light from its 

 polished surface ; a characteristic which is closely linked to its high 

 refringent power. That power indeed is so great, that it is approached 

 by no colourless solid, nor by any even of the highly refringent oils, 

 and inorganic compounds of carbon. Thus, a ray, on passing into 

 this substance is so bent from its course, that the new direction which 

 it takes is at any given point f nearer to the perpendicular on the 

 surface than was the distance of a corresponding point in the course 

 Vol.111. (No. 32.) r 



