

INTRODUCTION. 



hard, but softer than copper fahlers, and harder than copper 

 pyrites -, that amber is soft, and forms a medium between 

 soft and very soft fossils."* 



Not to mention the FRACTURE, FRAGMENTS, LUSTRE, 

 and TRANSPARENCY, which are described in the common 

 terms of most systems of mineralogy, it may be necessary to 

 add a few words concerning the other remaining character- 

 istic, namely, the WEIGHT. In this, as already mentioned, Weight. 

 a relative scale is proposed, instead of ciphers, which seldom 

 supply prompt or immediate ideas, especially as the reader 

 generally forgets the tables prefixed. The total dismission of 

 ciphers serves, at the same time, to render the arrangement 

 more uniform and harmonious. The Weight has been, by 

 many of Werner's disciples, confounded with the Specific 

 Gravity, which requires an operation, and does not belong to 

 the external characters of Werner ; while the Weight, with 

 some experience, may be estimated, as he says, by the hand. 

 His epithets, however, are in this instance particularly indis- 

 tinct, being Very light, Light, Rather heavy, Heavy, Very 

 heavy. His scale is also too brief, five degrees being neces- 

 sary for the gems and rocks, and five more for the metals. 

 For while the specific gravity of platina is about 21, gold 19, 

 silver 10, copper 8, iron about 7, and tin little inferior, 

 barytes only exceeds 4 ; so that there is a wide transition from 

 the heaviest stones to the metals, but not so great to the ores. 

 To the metals, therefore, another scale should be adapted for 

 common use. It is hoped that the one here proposed will be v 



found sufficient for the purposes of petralogy ; and it is, like 

 the other improvements, submitted to the discussions and 

 alterations of the intelligent in a science which is quite new 

 and daily progressive. 



3. Remarks on Werners Geognosy, or System of Rocks. 



From the sketch imparted by Daubuisson to Brochant, 

 and from Mr. Jameson's Geognosy, we are enabled to form an 



* Werner, Ch. Ext. p. 272. 



