16 DEPOSITS OF PHOSPHATE OF LIME. [bull. 46. 
tioned geological survey served only to show that the proportion of 
lime phosphate in the rocks is extremely variable, and that in certain 
beds it is so considerable that the material might advantageously be 
used in a local way for fertilizing purposes. 1 
The search for phosphatic materials in the stratified rocks demands 
a method of inquiry that has not yet been applied to the study of our 
rocks. It seems to me that the method, or rather methods, should be 
as follows: 
First, there should be a careful inquiry to determine the share in 
which the several important groups of rock-making organic forms con- 
tribute phosphatic matter to strata. This can be accomplished by care- 
fully comparing the chemical character of particular strata with the 
fossils the beds contain. When this determination is made we shall 
have one means of guiding our inquiries, which will surely be of great 
value in the search for bedded phosphates. 
Secondly, we should have a carefully executed chemical survey of our 
stratified rocks. Enough can be gathered from the scattered records of 
chemical analysis to make it plain that certain features of the chemical 
character of particular beds or divisions of strata often extend later- 
ally for great distances. This is shown in a general way by the char- 
acter of the soils formed of the waste of particular horizons ; for in- 
stance, the deposits of the horizon on which lies the Cincinnati group 
of this country and the equivalent deposits of Europe are nearly always 
well suited to grasses and grains and have a great endurance to tillage. 
It is now desirable to take these beds which promise to afford mineral 
manures and subject each stratum to analyses which shall determine the 
quantity of phosphoric matter, soda, and potash which they contain, so 
that their fitness for use as mineral manures may be ascertained. 
Below the level of the Silurian and Cambrian strata, and partly in 
those sections where they have been much metamorphosed, lies the field 
of the vein phosphates. It is more than likely that in this vast thick- 
ness of rocks with their development in this country there are many 
extensive sources of this class of phosphates which await discovery. 
As yet no careful search has been made for such veins in any part of 
the United States. The regions most likely to contain such deposits 
are found in the central parts of the Appalachian system of mountains, 
1 Among the analyses recently made by the chemists of the Kentucky geological 
survey is one which indicates the presence of phosphoric acid in considerable quan- 
tities in the limestones of Coruiferous age exposed at Stewart's mill, on Lulbegrud 
Creek, in Clark County. This partial analysis, for which I am indebted to Mr. John 
R. Proctor, the present director of the Kentucky survey, is as follows, viz: 
Lime carbonate - 21. 380 
Magnesia 3. 055 
Phosphoric acid 9. 710 
Potash 830 
Soda 228 
Siliceous nodules insoluble in acids 27. 580 
(490) 
