Mr. Grcville Williams on Emeralds and Beryls. 32 i 



The coal-gas having been lighted and the oxygen turned on, the 

 beryl at once begins to melt, and froths or, rather, boils violently. 

 By careful regulation of the supply of oxygen, the boiliug entirely 

 disappears ; but the slightest excess of oxygen causes it to be 

 renewed. This property of oxygen, which is found to occur with 

 other substances besides beryls and emeralds, I hope to study in 

 greater detail. Having so adjusted the name that the beryl fuses 

 tranquilly, and is yet at the exact point of maximum heat (if the 

 substance is not too large for the apparatus), it no longer lies as a 

 shapeless mass on the carbon support, but gathers together, rises up, 

 and forms a perfect bead — round, clear, and brilliant. To obtain 

 the adjustment of position necessary for this result, it is indispen- 

 sable to wear very dark glasses, so dark, indeed, that objects can 

 scarcely be discerned through them in bright daylight. Without 

 this precaution, the minute details of the globule cannot be observed, 

 and it would be impossible to drive away the bubbles, which form 

 instantly when the bead is moved in the slightest degree from the 

 proper position. The heat and glare would also soon seriously affect 

 the sight ; and, with every precaution, I have found, after the pre- 

 paration of one or two hundred globules, that my sight appears 

 (even after an interval of some months) to be slightly but deci- 

 dedly deteriorated. If all is working properly, the bead should be 

 quite mobile ; and advantage of this must be taken to keep it in- 

 cessantly rolling, and yet not remove it from the point where it 

 gives out the most brilliant light. By this means the whole glo- 

 bule is rendered transparent. If, on the other hand, it is allowed 

 to remain without motion on the carbon (unless the globule be very 

 minute), it will be found, when cold, to have a white opaque base, 

 passing into the centre of the bead in a conical form, and entirely 

 destroying its beauty. This exact adjustment of the position of 

 the bead at the point of maximum heat, combined with constant 

 movement of the carbon support and perfect regulation of the 

 proportions of oxygen and hydrogen, are indispensable to the pro- 

 duction of the glasses, specimens of which accompany this paper. 



"When thus fused, the globules obtained from the beryl A were 

 clear and colourless, but generally contained a few minute air- 

 globules and stria), which become obvious under the lens. Towards 

 the end of this part of the investigation I succeeded in almost 

 entirely avoiding these defects ; but I have been compelled for a 

 time to abandon experiments in this direction in consequence of 

 the strain thrown upon the eyes. 



When chromic oxide is added to the beads, and they are again 

 carefully fused, they acquire a fine green colour ; the tint, how- 

 ever, is inferior to that of the emerald. The green beads may, by 

 an intense and prolonged heat, be rendered colourless. With 

 cobalt oxide the beads afford beautiful blue glasses of any desired 

 shade ; and in all cases the results are the same as with the arti- 

 ficial mixture of beryl ingredients to be described further on. 



The effect of fusion upon the beryl is to lessen the hardness 

 and lower the specific gravity. The globules may be scratched by 

 Phil. Mag. S. 4. Vol. 46. No. 306. Oct. 1873. Z 



