200 
THE GEOLOGIST. 
brown colour, and holding in solution an iilmic compound, wliicli 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 
degrees (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 entii^ely in accordance with the observations 
of the celebrated Regnault upon the subject. 
2. The first degTce 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 
xyloid lig-nite, 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 natm'e 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 degTee 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 recog-nized 
by geologists. 
In concluding M. Fremy expresses an opinion to the effect that the 
substances which we have been considering are far fi'om 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 these varieties in the different kinds of coal, or in the same 
bed even, M. Fremy proposes to examine in a fiitm-e communication. 
