318 BOTANY AND PALAEONTOLOGY 



Arkansas, is exposed on Little Cypress Creek, Dallas county, on the pro- 

 perty of Mr. Watson. It crops out on the nearly perpendicular and much 

 disturbed bank of the creek, is one to two feet thick, sometimes black and 

 a compound of pure combustible matter much softer than stone coal or 

 true coal, sometimes formed of alternate layers of soft clay with bands of 

 black and pure lignite, from one to two inches thick. There are apparently 

 two beds of lignite exposed on this bank. The one, nearly at the top of 

 the bank, is overlaid by one foot of black soft clay covered with about 

 twenty feet of argillaceous sand. The other exposed a little lower down 

 the creek appears separated from the former by nine feet of soft plastic 

 clay without plants. As the bank has been much disturbed by the erosions 

 of its soft parts, which have caused slips and local subsidences, it is still 

 possible that there is only one bed of lignite formed there, parts of which 

 have accidentally been broken off and dropped down the declivity of the 

 bank. 



In counties where wood is still abundant, beds of tertiary lignites are 

 perhaps, for the present, of nojgreat value. Nevertheless, when the com- 

 bustible mineral is pure, the amount of carbon which the matter con- 

 tains is always greater than it is in wood. Following the analysis of two 

 specimens of lignite of Green county,* the amount of carbon in the 

 matter is fifty-three to fifty-seven per cent., when the carbon of wood 

 does not amount to more than forty to forty-five per cent. Thus, these 

 beds of lignites may become valuable in the future, especially for the navi- 

 gation of the steamboats on the rivers. 



As beds of lignite, found in the southeastern part of Arkansas have been 

 taken sometimes for strata of true mineral coal by persons unacquainted 

 with the distribution of the geological formation, it is well to present in a 

 single table, and for comparison, some of the fossil leaves which are gene- 

 rally found in connection with these beds of recent origin. All the leaves 

 found fossil in the Tertiary, recall forms which we are in the habit of 

 seeing around us on the trees of our time. Most of the genera, even some 

 of the species are the same. Thus we have with the lignitic formation, 

 fossil leaves of the oaks, walnuts, beeches, magnolias, elms, and others ; 

 mostly leaves of Dicotyledonous trees, easily recognized by the branching 

 of the veins. On the other hand, the fossil leaves of the true coal are 

 mostly ferns, and the other remains represent the scars on the striae of the 

 bark of trees of which the form, the direction and the remarkable 

 regularity is entirely at variance with the rough and irregular surface of the 

 bark of our trees. (See PI. 3, fig. 1, 2, and 3.) 



The leaves figured on Plate VI were not found in the tertiary strata of 

 Arkansas. The time of exploration was too short to permit researches 



* 1st volume of the Report, p. 177. 



