164 
GEOLOOT OF NORTH CAROLINA. 
dance. Thus lime is furnished by limestone, magnesia by dolomite and 
by talc, serpentine, &c. 
The other elements of mineral origin, phosphorus, sulphur and chlo- 
rine, are derived from other mineral species which are universally dif- 
fused, though in very small quantities, as phosphorus from apatite, sulphur 
from pyrite and from gypsum, chlorine from common salt and from apa- 
tite, &c. Thus it is evident that soils will vary indefinitely in com- 
position and fertility according to their source in the mineral kingdom. 
And thus also the bearing of geology upon agriculture becomes obvious. 
From the previous general description, and from the preceding account 
of the geology of the State, it is apparent that the range of its soils is. 
such as to include almost every variety and grade. 
The plan of the Survey includes as complete an investigation of these 
soils as is practicable. It is proposed to analyze the soils in connection 
with the underlying rocks, and to classify and map them. Meanwhile 
the soils have been graded in a preliminary way, over a large part of the 
State, the estimation being based upon natural growth, physical charac- 
ters and actual yield. As soon as practicable a map of these observations 
will be published. Some progress has also been made in the work of 
systematic analysis, according to the general plan. Nothing like a com- 
plete discussion of these analyses, or a general classification of the soils of 
the State upon the basis of their results, can be attempted at this stage of 
the work. But for the benefit of those who are not familiar with the 
subject of soil analysis, and the relations of chemical composition to fer- 
tility, and the most common and obvious causes of infertility, and the 
methods of removing it, so far as indicable by chemistry, and in a word, 
the function and value and limits of analysis in practical agriculture, the 
following table is given as furnishing standards of comparison. 
