FIXITY OF PHYSICAL PROPERTIES. 251 



companions had received a quantity of pieces of 

 amber, and was relating to Werner, then very 

 young, that he had found in the lot one piece from 

 which he could extract no signs of electricity. 

 Werner requested to be allowed to put his hand in 

 the bag which contained these pieces, and imme- 

 diately drew out the unelectrical piece. It was 

 yellow chalcedony, which is distinguishable from 

 amber by its weight and coldness. 



The principal external characters which were 

 subjected by Werner to a systematic examination, 

 were colour, lustre, hardness, and specific gravity. 

 His subdivisions of the first character (Colour,} were 

 very numerous ; yet it cannot be doubted that if we 

 recollect them by the eye, and not by their names, 

 they are definite and valuable characters, and espe- 

 cially the metallic colours. Breithaupt, merely by 

 the aid of this character, distinguished two new com- 

 pounds among the small grains found along with 

 the grains of platinum, and usually confounded with 

 them. The kinds of Lustre, namely, glassy, fatty, 

 adamantine, metallic, are, when used in the same 

 manner, equally valuable. Specific, Gravity ob- 

 viously admits of a numerical measure ; and the 

 Hardness of a mineral was pretty exactly defined 

 by the substances which it would scratch, and by 

 which it was capable of being scratched. 



Werner soon acquired a reputation as a minera- 

 logist, which drew persons from every part of Europe 

 to Freiberg in order to hear his lectures ; and thus 



