404 



BURNING GLASS. 



What is remarkable with regard to experiments on iron, is, that 

 the lower part, i. e. tiiat part in contact with the charcoal, was 

 first melted, when thai part which was exposed to the focus re- 

 mained unfused : an evidence of the effect of (lux on this metal. 



Several of the semi.crystalline substances, exposed to the focal 

 heat, exhibited symptoms of fusion : such as the agate, oriental 

 flint, cornelian, and jasper ; but as the probability is, that these 

 substances were not capable of complete vitrification, it is enough 

 that they were rendered externally of a glassy form. Garnet 

 completely fused on black-lead in 120", lost |th of a grain, became 

 darker in colour, and was attracted by the magnet. Ten cut gar. 

 nets taken from a bracelet, began to run the one into the other in a 

 few seconds, and at last formed into one globular garnet. The 

 flay used by Mr. Wedgwoo'l, to make his pyrometric test, run in 

 a few seconds into a white enamel. Seven olher kinds of clay 

 seat by Mr. Wedgwood, were all vitrified. Several experiment* 



