17g GEOLOGICAL RECONNOISSANCE 



No. 39. Lignite, from same locality as No. 38. 



Color dark grayish-brown; woody structure only partly preserved, in- 

 distinctly laminated; fracture dull; may be cut with a knife, cut surface 

 shining. 



Composition, dried ot 212 to 220 deg. F: 



Volatile matter 31.903 



Fixed carbon (charcoal) 53.737 



Ash 14.300 



100.000 

 The air- dried lignite lost 12.774 per cent, of moisture at 220 deg. F. 



A qualitative examination of the ash showed the presence of clay (pre- 

 ponderating) and silica, sulphate of lime, iron, alumina, and potassa. 



The small amount of ash which these lignites contain, would make 

 them useful as fuel, if timber were scarce in that part of Arkansas where 

 they occur, or as a substitute for stone-coal, in cases where the use of the 

 latter is preferable to that of wood. 



NITRE EARTHS. 



Of the samples of nitre earth which were collected on the first geo- 

 logical excursion, I made a complete analysis of only one; two have been 

 analyzed by Dr. Owen,* who determined all the various constituents 

 directly, with the exception of the nitric acid, the quantity of which 

 was estimated by the loss. The importance of the subject made it 

 appear desirable to have a direct determination of this acid in the two 

 samples referred to; they are given in Nos. 41 and 42. For the method 

 employed, see "methods of analysis," p. 190. 



No. 40. Nitre earth; labeled "white nitre earth formed from decompo- 

 sition of bottom rock, Marion county." 



A soft, calcareous earth, of pale yellowish-red color, feeling slightly 

 gritty between the fingers; of sandy appearance, containing fragments of 



* See Dr. Owen's Report. 



