248 Sir David Brewster on the Structure 



fore conclude my paper by expressing a hope that this im- 

 portant mineral may meet with more able investigation." 



This discovery of a new matrix of the diamond takes away 

 the foundations of the argument from which I concluded 

 ¥ that the compressible state of the diamond could not arise 

 from heat," for it is possible that the rocky matrix in which it 

 was found had an igneous origin ; and Captain Franklin's 

 supposition that it might be fused under compression, is quite 

 conceivable. 



But, though I admit the possibility of the diamond having 

 been in a state of igneous fusion, I consider it highly impro- 

 bable that it was so. In the laborious examination, which I 

 carried on for several years, of the cavities in topaz, quartz, 

 amethyst, chrysoberyl, &c, and in salts formed from aqueous 

 solutions, I had occasion to observe the condition of many 

 thousands of cavities, and in no one case, neither in crystals 

 which exist in rocks known to be of igneous origin, nor in 

 crystals artificially formed, have I been able to discover a 

 single cavity in which the expansible fluid which it contained 

 had compressed the surrounding mass, and communicated to 

 it the polarizing structure existing around the cavities in the 

 diamond. 



Now, in glass which is known to have been in a soft state, 

 and in amber, which is generally allowed to be an indurated 

 gum, I have discovered cavities similar to those in the dia- 

 mond, and surrounded by the same polarizing structure; a 

 structure which could only be produced by a compressing 

 force emanating from these cavities. 



As I am desirous that mineralogists should thoroughly un- 

 derstand the nature of this structure, I have made two draw- 

 ings of the diamond Laske which contains the cavities under 

 consideration. 



Fig. 1. 



