167 



Art. XIV. MuceUamous Intelligence* 



I. Mechanical Science. 



§ Optic?, the Arts, |c. 



1 . On the Structure of the Diamond. — Whilst making ex- 

 periments on the optical structure of amber. Dr. Brewster was 

 led to compare it with the diamond. He found some singular 

 analogies in the two substances, but one diamond which he ex- 

 amined presented a new phaenomenon of a most unexpected 

 kind, which Dr. Brewster observes, is the only fact in the na- 

 tural history of this body that promises to throw light upon its 

 origin and mode of formation. The same phsenomenon occurs 

 also with amber. It is " the existence of small portions of air 

 within both substances, the expansive force of which has com- 

 municated a polarizing structure to the parts in immediate con- 

 tact with the air. This structure is displayed by four sectors of 

 polarized light encircling the globule of air, and can be pro- 

 duced artificially either in glass or in gelatinous masses, by a 

 compressing force, propagated circularly from a point. It is ob- 

 vious that such an effect cannot arise from any mode of crystal- 

 lization ; and if any proof of this were necessary, it might be 

 sufficient to state, that I have never observed the slightest trace 

 of it in more than 200 mineral substances which I have ex- 

 amined, nor in any of the artificial salts formed from aqueous 

 solutions. It can, therefore, arise only from the expansive 

 force exerted by the included air on the diamond and tile arn- 

 ber, when they were in such a soft state as to he susceptible of 

 compression from so small a force. That this compressible 

 state of the diamond could not arise from the action of heat is 

 manifest from the nature and the recent formation of the soil tk 

 which it is foimd ; that it could not exist in a mass formed by 

 aqueous deposition is still more obvious ; and hence we are led 

 to the conclusion, rendered probable by other analogies, that the 

 diamond originates like amber from the consolidation ofjperhaps, 

 vegetable matter, which gradually acquires a crystalline form by 

 the influence of time, and the slow action of corpuscular forces." 



