138 On the Jffinities of 



II. Fifty grains of this roasted quartz were pulverized 

 arid mixed with 3 grains of lamp black. The colour of 

 the mixture was blueish black. 1 exposed it in a Cornwall 

 clay pot to 170° of Wedgwood; but found the contents 

 unfuscd, and still pulverulent. The mixture had become 

 nearly of a black colour, but the fragments of silex re- 

 mained unchanged. 



III. Fifty grains of roasted quartz, mixed with half a 

 grain of lamp black, were exposed in a similar manner as 

 No. II. The result was the quartz in as pure and unfused 

 a state as when introduced. The half grain of lamp black 

 was nearly dissipated, and had communicated a shining lead 

 colour to the interior of the crucible. 



IV. A crystal of quartz possessing great depth of water 

 was found xo weigh 36£ grains. It was afterwards, for six 

 hours, exposed in a bright red heat ; when it was found to 

 have lost nearly half a grain. The lustre and shape of the 

 crystal remained unchanged. 



V. The same crystal, after losing a small fragment, 

 weighed 35^ grains. It was then exposed to 168° of Wedg- 

 wood. It was found shivered into a number of small pieces 

 of a pearly white colour tinged with blue. A few fragments 

 still possessed their original angle and transparency. The 

 whole were carefully collected, and weighed only a quarter 

 of a grain less than when introduced. In this experiment 

 a total change was effected upon the subject, but scarcely 

 any less of weight could be reckoned. 



VI. I took two crystals of quartz, weighing 42 grains, 

 and introduced them into a Cornwall clay crucible filled 

 with charcoal, The heat to which they were exposed was 

 nearly 1 70°. When examined, the following was found to 

 be the result, The crucible was found still nearly filled 

 with charcoal. The two crystals, with the exception of one 

 small fragment, remained entire, though fritvered a good 

 deal. Excepting where the charcoal had entered the fissures, 

 there was not the most distant appearance of contact, or any" 

 combination betwixt the siliceous matter of the quartz and 

 it. The crystals had entirely lost their transparency, were 

 possessed of a whitish enamelled surface, and seemed spongy 

 an the centre. Their weight was 41 grains; and if the 

 small portion of carbonaceous matter be taken into the ac- 

 count, which had entered the fissures, not more than 3^4ths 

 of a grain was lost, of weight, in the exposure. This expe- 

 riment proves that the combination of carbon with the mat- 

 ter of silex and clay, which constitutes quartz, takes place 

 at a higher temperature than 170" of Wedgwood, and ren- 

 ders 



