420 



Progress in Science. 



[July, 



taken up, and the bead treated as before, when cold, the colour is a murky 

 reddish purple, and the spe&rum no longer giving the band in the red, but two 

 obscure absorption-bands, very close together, and a slight shading at f, as 



r IE D B 



Fig. i. 



Fig. 2. 



Fig. 3. 



Fig. 4. 



Fig. 



Fig. 6. 



Fig. 7. 



Fig. 8. 



Fig. g. 



shown in Fig. 1. Upon adding 4 percent of soda the bead becomes quite 

 clear and paler, showing the same spectrum, but while hot showing the band a, 

 as in Fig. 2. A further addition of 10 per cent of sodium carbonate causes 



