MINERAL INDUSTRIES OF THE UNITED STATES FERTILIZERS. 7 
bone and is present also in the brain and associated nervous matter. 
To man, therefore, it is particularly important. Soils containing no 
compounds of phosphorus or else depleted of those once present, de- 
mand an addition of such material to be productive. 
The basis of commercial fertilizers and the ingredient of greatest 
bulk to which the other more concentrated constituents are added, is 
an impure compound of phosphorus occurring in nature in large 
masses and known as phosphate rock. The United States is the 
world’s greatest producer of this material, and within her borders 
lie the largest reserves thus far discovered. Some 10 years ago the 
quantity of phosphate rock in sight throughout the world was not 
sufficient to meet the growing agricultural needs for 100 years, and 
the situation was said to represent 66 man’s weakest hold on the 
universe ” ; but the recent discovery of our western phosphate fields 
and an appreciation of the size of deposits in northern Africa have 
extended this limit many centuries hence. 
There are other sources of the phosphorus content of fertilizers, 
among which organic substances such as fish scrap, cottonseed meal, 
bones, slaughterhouse refuse (prepared and sold in a form called 
tankage), and guano are the most important; but most of these sub- 
stances are in strong demand for other purposes, and the growing 
price is fast reducing their economic availability for fertilizer manu- 
facture. This, too, in spite of the fact that most of them have also a 
nitrogen content and therefore perform a double function when 
added to fertilizers. 
At the outbreak of the European war, we were obtaining from 
abroad, in addition to a small importation of phosphate rock, incon- 
sequential supplies of two other phosphatic products. These were 
basic or Thomas slag and the mineral apatite. Basic slag is a by- 
product from the smelting of iron ores rich in phosphorus, by a 
process which relegates this usually deleterious constituent to a mass 
of slag which is thereby so enriched in phosphorus that it can be 
ground and used as a fertilizer. This process has developed prin- 
cipally in Europe, where large deposits of phosphorus-rich iron ore 
have been rendered available by it; in fact, the iron supply of Ger- 
many is drawn largely from such deposits in Lorraine, divided be- 
tween German Lorraine and captured French Lorraine, which have 
also furnished most of the phosphate fertilizer used in Germany 
since the supply of phosphate rock from the United States was 
cut off. Apatite is a mineral mined to a limited extent in Canada; 
but its deposits are too restricted in size ever to be significant, in 
spite of the fact that scattered microscopic crystals of apatite are 
present in practically all igneous rocks and represent the ultimate 
source of the phosphoric acid or soils as well as of that now found 
concentrated in phosphate rock. 
