periment, 1 hardly know any which I should prefer to this of Mr. 

 Klaproth's. According to the opinion offered, this substance should 

 contain bitumen, into the composition of which carbon enters, in 

 an abundant proportion and, by the experiment, an effect is pro- 

 duced which excites the astonishment of this excellent chemist; 

 because it is that effect, which he would have expected from the 

 presence of charcoal ; which he had no conception entered into 

 the composition of the substance which was the subject of his 

 experiment. Having obtained this satisfactory evidence, from the 

 analysis of the semi-opal ; the task remains to ascertain, whether 

 any traces of the substance are to be discovered, in the opal itself. 



The OPAL, opal edler, gelber opal, Werner, the noble opal of 

 some, and the oriental opal of thjk jewellers, in addition to the 

 general characters which distinguish this class of fossils, possesses 

 the astonishing property of displaying, in a strong light, the most 

 vivid and beautiful colours, which continually play on the eye, with 

 varying splendour, on the least change of position. From that 

 spot which, the instant before, showed a beautifully bright green, 

 or purple, a rose-cotoured flame suddenly darts forth, forming what 

 the amateurs of this stone term, the jire of the opal. But descrip- 

 tion can furnish only a very imperfect idea of the brilliant display 

 of colours yielded by this admirable, and inestimable jewel. Our 

 admired poet Thomson, indeed, appears to have succeeded, as far 

 as the powers of language could enable him. It is in his address 

 to the Sun, where he thus speaks of the wonderful properties of this 

 highly elaborated work of nature. 



The unfruitful rock itself, impregn'd by thee, 

 In dark retirement forms the lucid stone: 

 The lively Diamond drinks thy purest rays, 

 Collected light, compact, that polish'd bright, 

 And all its native lustre let abroad, 

 Dares, as it sparkles on the fair one's breast, 



