200 



THE GEOLOGIST. 



brown colour, and holding in solution an ulmic compound, which is 

 easily deposited by the addition of water. 



M. Fremy states, parenthetically, that in connection with this sub- 

 ject he has exposed woody tissue to a temperature of two hundred 

 decrees (Cen.), for several days, and has noticed several modifications 

 successively take place, producing substances quite comparable to 

 those found in the lignites— the first changes resembling the xyloid ; 

 the latter the compact lignites — resisting the alkalis, and yielding 

 readily to the hypochlorites. 



M. Fremy then sums up the results of his observation as follows : 



1. The chemical characters of the combustible minerals subjected 

 to the reagents pointed out are effaced by age ; and the organic 

 matter resembles graphite the more as the rock from which it is 

 taken is older. An exception, however, must be made in the altered 

 rocks. This result is entirely in accordance with the observations 

 of the celebrated Regnault upon the subject. 



2. The first degree of alteration of woody tissue, represented 

 by peat, is characterized by the presence of ulmic acid, and also 

 woody fibres and the cells of the medullary rays, which can be 

 purified and extracted in great quantity by means of azotic acid and 

 the hypochlorites. 



3. The second degree of modification corresponds to fossil wood or 

 xvloid lignite, which is in part soluble like the preceding body in the 

 alkalis ; but its alteration is more marked, for it is dissolved almost 

 entirely in nitric acid and the hypochlorites. 



4. The third stage of alteration is represented by perfect lignite, 

 which the reagents tell us already partakes of the nature of coal, — 

 in consequence, therefore, the alkaline solutions generally do not act 

 upon it, although it is completely soluble in the hypochlorites and 

 nitric acid. 



5. The fourth degree of modification corresponds to coal, which is 

 insoluble in alkaline solution and the hypochlorites. 



6. The fifth state of alteration is shown by anthracite — which 

 evidently resembles graphite — resisting the reagents which acted upon 

 the preceding combustibles, as we have seen, and being attacked but 

 slowly by nitric acid. 



From this it will be seen that the chemical reagents employed by 

 M. Fremy confirm the classification of combustible minerals recognized 



by geologists. 



In concluding M. Fremy expresses an opinion to the effect that the 

 substances which we have been considering are far from being the 

 only modifications which the organic matter undergoes in its changes 

 to the combustible minerals : he thinks that there are intermediate 

 transformations of the organic tissues, which correspond to the differ- 

 ences which are noticeable in the different kinds of coal and lignite. 



The question whether the reagents are sensible enough to charac- 

 terize 11 lese varieties in the different kinds of coal, or in the same 

 bed even, M. Fremy proposes to examine in a future communication. 



