324 



Royal Society 



proportions used : — 



Silica 67'5 



Alumina 18"5 



Glucina 140 



100-0 

 I did not introduce any iron or magnesia, as I regard theni as ac- 

 cidental impurities varying in amount. 



When a mixture of the above composition is exposed to the 

 flame of the oxyhydrogen blowpipe, it fuses with almost exactly 

 the same phenomena as with the natural beryl. It is, however, as 

 might be anticipated from the absence of iron and chromium, much 

 easier to get a colourless transparent bead with the mixture than 

 with either emeralds or beryls. The greatest difficulty in this 

 respect is, of course, found with emeralds. The specific gravity of 

 the fused globules was determined, with the following result : — 



Specific Gravity of Artificial Amorphous Beryls. 



No. of experi- 

 ment. 



W. 



W\ 



t. 



pt. 



D. 



I. 



•5774 



•3394 



o 



13 



•999430 



2-42 



or almost exactly the same as the density of native emeralds and 

 beryls after fusion. 



When a small portion of chromic oxide is added to the artificial 

 mixture and the whole is subjected to fusion, the resulting bead is 

 of a rich yellowish green, and in many experiments approached to 

 the emerald tint ; but, as a rule, the colour is more of a faded leaf- 

 green ; and although I have never obtained a globule of the vivid 

 tint of a fine emerald, the glasses, when well cut, are quite beau- 

 tiful enough to serve as jewels. Prolonged heating gradually 

 diminishes the colour, the bead gradually becoming of the palest 

 bottle-green, and, finally, nearly colourless. This result is the same 

 as with the emerald. 



The metallic oxide which yields the finest tints when fused 

 with opaque beryls, or the artificial mixture, is that of cobalt. 

 The manner in which this oxide withstands the intense heat of the 

 oxyhydrogen flame is remarkable. All tints, from nearly black to 

 that of the palest sapphire, can be obtained ; and the resulting 

 glasses, when cut, are extremely beautiful, and have almost the 

 lustre of crystallized gems. 



The globules obtained by fusing the artificial mixture of beryl 

 ingredients with didymium oxide show the characteristic absorption- 

 spectrum of that metal in a very perfect manner, the lines being 

 intensely black. Even when the bead is quite opalescent from 

 insufficient heating, the black lines are beautifully distinct in the 

 spectroscope. With a large quantity of didymium oxide the beads 

 are of a lively pink, becoming more intense by artificial light, and, 

 when cut, form very pretty gems. The presence of didymium in 

 sufficient quantity raises the specific gravity. 



