'206 ANNUAL OF SCIENTIFIC DISCOVERY. 



combustible. Thus a distinction is immediately established between 



ff 



fossil-wood and compact lignite. 



I have always observed that the lignites which resist the action of 



V ^J 



potash are those which, by their bearing, approach nearest to the 

 coal series. 



Compact lignites, black and brilliant like coal, dissolve entirely in 

 alkaline hypochlorites, are rapidly attacked by nitric acid, and pro- 

 duce the yellow rosin which I have already mentioned while treat- 

 ing of fossil-wood lignite. 



The two characters just indicated prevent, then, the confounding 

 lignites with coals. Coal, in fact, is not dissolved by hypochlorites, 

 and is attacked but feebly by nitric acid. I have submitted to the 

 test of the hypochlorites almost all the important coals belonging to 

 different strata, and have found that these combustibles always resist 

 the action of these chemical re-agents. To me this characteristic ap- 

 pears so valuable that I think were a sample of coal met with slightly 

 attackable by hypochlorites, it would be advisable to examine whether 

 the combustible possessing this exceptionable property were really 

 coal ; for it may well be imagined that in coal-fields there may exist 

 vegetable matters unequally decomposed. 



Coal and anthracite which resist the action of alkaline and hypo- 

 chlorite solutions dissolve completely in a mixture of monohydrated 

 sulphuric acid and nitric acid ; the liquid takes a very deep brown 

 color, and holds in solution an ulmic compound, which water com- 

 pletely precipitates. 



It is not my intention in this paper to consider the influences by 

 which organic tissues are transformed into combustible minerals. I 

 ought, however, here to put on record what seems to me an inter- 

 esting observation. I have ascertained that ligneous tissue, exposed 

 for several days to a temperature of 200, undergoes successive modi- 

 fications, and yields bodies very similar to those found in lignites. 

 The first are soluble in alkalies, and correspond to fossil-wood lig- 

 nite ; the second are insoluble in alkalies, but dissolve entirely in 

 hypochlorites, like compact lignite. These are the new facts which 

 it is my wish to submit to the Academy. Their evident object is to 

 introduce chemical characteristics into the study of combustible min- 

 erals, and they appear to me to lead to the following deductions : 



1. By treating combustible minerals by the above-mentioned re- 

 agents, it is ascertained that in proportion to the age of the lignite, so 

 the chemical characteristics of the tissues gradually disappear, and 

 the organic matter more resembles graphite, the older stratum whence 

 it is derived. One exception I make in respect of the strata which 

 have been modified under the influence of metamorphism. My 

 researches accord completely with those of M. Regnault, who has 

 already arrived at the same conclusions as myself in his important 

 researches on combustible minerals. 



2. The first degree of modification of ligneous tissues, represented 

 by turf, is characterized by the presence of ulrnic acid, and also by 

 the ligneous tissues or cellules of the medullary rays, which can be 

 extracted and purified in considerable quantities by means of nitric 

 acid or of hypochlorites. 



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



