178 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 Matters .0 sei ae tees Case w es Ve 31.963 
Fixed carbon (charcoal) «++ ++ +ees seer eeee 53.737 
AGH. RAS sa iw CON CAN swe eRe NAS Sew 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. 
