FERTILIZERS— AN INTERPRETATION OF THE SITUA- 
TION IN THE UNITED STATES. 
By Joseph E. Pogue, 
Of the Division of Mineral Technology, United States National Museum. 
INTRODUCTION. 
Eighty-odd chemical units or elements are known which singly or 
in various combinations make up all objective things. Certain of 
them are essential to life, as entering into the constitution of the body 
itself ; others are necessary to the upward development of life in that 
they comprise those materials through the use of which evolving man 
has developed his mentality; still others seemingly play no part in 
human affairs. 
The first are chiefly products of the soil and come to man in the 
form of food; the second are products of the rocks and are obtained 
by man in the form of minerals ; the third have no apparent use, and 
we are not concerned with them here, however interesting might be 
speculations as to their significance. 
In the final economy of nature, therefore, those chemical elements 
that enter into the food supply are of fundamental importance, while 
next to them are those which, combined as mineral products, have 
been employed by mankind in building his civilizations. 
At the outset primitive man was predatory, living chiefly on other 
animals. He was, therefore, not immediately concerned with the 
products of the soil, although ultimately and indirectly his suste- 
nance came from that source. At a later stage, however, he turned 
his attention to the raising of crops and thereby made possible a 
permanence in settlement and increase in population not attainable 
under the precarious and shifting circumstances of an exclusive game 
supply. It is now regarded as a long step upward in the progress 
of man when he started his first crude attempts at agriculture. 
Whether early man so viewed it himself is doubtful, inasmuch as this 
form of activity was to him ignoble and therefore relegated to 
women, the aged, and the infirm. 
Many thousands of years have passed since the first simple be- 
ginnings in agriculture. Progress was made, very notable progress 
