204 ANNUAL OF SCIENTIFIC DISCOVERY. 



Britain independent of the world for dyestuffs ; and it is more than 

 probable that England, instead of drawing her dyestuffs from foreign 

 countries, may herself become the centre from which all the world 

 will be supplied. 



Colors of Gems. It is also an interesting fact that M. Tournet, 

 of France, has lately demonstrated that the colors of gems, such as 

 the emerald, aqua-marina, amethyst, smoked rock crystal, and others, 

 are due to volatile hydro-carbons, first noticed by Sir David Brew- 

 ster in clouded topaz, and that they are not derived from metallic ox- 

 ides, as has been hitherto believed. Address Pres. British Associ- 

 ation, 1861. 



CHEMICAL RESEARCHES OX COMBUSTIBLE MINERALS. 



The following important contribution to Chemical Geology was re- 

 cently communicated to the Paris Academy by the well-known chem- 

 ist, Fremy: 



My long-pursued studies on vegetable tissues, of which the Acad- 

 emy already knows the principal results, have naturally led me to 

 wish to determine the chemical characteristics of the combustible 

 minerals, and to try to discover whether their constituent materials 

 present any analogy with those forming unaltered vegetable tissues. 



Admitting, as do all geologists, that turf, lignite, coal, and anthra- 

 cite, are formed under different circumstances, and that they apper- 

 tain to the strata of different epochs, my desire is to discover in these 

 combustibles the degree of alteration of the organic tissue. 



In studying turf, I have discovered no really new fact. By the 

 side of the unaltered elementary organs, found in such large quanti- 

 ties in fibrous turf, I have found, according to the degree of altera- 

 tion the combustible has undergone, various proportions of those 

 brown compounds, neutral or acid, nitrogenized or not, which in our 

 ignorance we designate by the general term of uhnic compounds. 



The presence of these bodies, which M. Payen had already investi- 

 gated, establishes a very clear distinction between turfs and unaltered 

 organic tissues. 



The chemical examination of lignites was likely to prove more in- 

 teresting. In this examination I have taken care to distinguish those 

 specimens still presenting a ligneous organization from those which 

 have the appearance and compactness of coal. The former consti- 

 tute the xyloid lignite, or fossil-wood ; the latter, compact and perfect 

 lignite. Regarding their chemical characteristics, all the varieties of 

 lignite I have examined are included in the two preceding species. 



Although the fossil-wood lignite has often the tenacity and appear- 

 ance of ordinary wood, I have come to the conclusion that in this 

 combustible the ligneous tissue undergoes a great change ; trituration 

 reduces it to a fine powder ; submitted to the action of a weak solu- 

 tion of potash, it yields to the alkali a considerable quantity of ulmic 

 acid. 4 



The following two reactions establish a very marked difference 

 between ordinary wood and fossil-wood lignite : When nitric acid, by 

 the aid of heat, reacts on wood, it dissolves a portion only of its fibres 

 and rnedullar rays, and leaves untouched the cellulose matter, which 



