226 GEOLOGICAL RECONNOISSANCE 
out increasing its strength by passing it through hoppers, containing fresh 
earth; if so, the expense for fuel is unnecessarily increased. To evaporate 
the lye in the'most economical manner, it should be brought to the 
strength of 12 or 14 deg., by passing it repeatedly through fresh earth, in 
order to extract the soluble salts. A very useful instrument for ascer- 
taining the strength of the lye, is the saltpetre hydrometer. 
The best method of arranging the lixiviating troughs, or casks, is to 
place them at such heights, one above the other, that the lye passing 
through the first shall run into the second, and so continue, until the requi- 
site per centage of saltpetre is obtained, before proceeding to the boiling and 
graining process. Jn lixiviating, no more water should be used than is 
actually necessary to extract the nitre; and lye, under 12 or 14 deg. of the 
hydrometer, should be returned through fresh earth, before boiling, until 
that strength is obtained. 
There can be no doubt that works properly constructed, and judiciously 
and systematically managed, will produce salt-petre sufficient to make ita 
remunerative business. The location isimmediately on White river, which 
is navigable atall times, as high up as Jacksonport, and, for a small class of 
steamboats, during the greater portion of the year, up to the caves. The 
mouth of the cave is so close to the river bank, that, by means of a chute, 
the earth can be very conveniently projected to the river, where the water 
for lixiviation can be easily obtained. Fuelis close at hand, and will cost 
but the chopping and transportation. 
For further information, in regard to the geology of this county, as well 
as for the particulars of the analysis of the nitre earth, see the Neport of 
Dr. D. D. Owen, State Geologist, and also that of the Chemical Assistant, 
Dr. William Elderhorst. 
CRAWFORD COUNTY. 
After separating from you at Van Buren, I proceeded to examine the 
coal, on Frog bayou, owned by Mr. Phillips. The principal opening is on 
the west half of south-west quarter of section 18, township 19 north, 
range 30 west, being one mile south of the stage road leading from Van 
Buren to Little Rock. The same scam is also opened, on this bayou, 
about one mile north of the stage road. This coal, known as the * Phillips 
bank,” is one foot thick, it has a semi-metallic lustre, and though easily 
mined in large blocks, its cohesion is so slight that it soon breaks into 
small lumps by handling. It is the principal coal used by the blacksmiths 
iu the southern part of Crawford, and the greater part of Franklin county, 
