12 BULLETIN 102, PART 2, UNITED STATES NATIONAL MUSEUM. 
deeply with other sources of supply. The largest source of fertilizer 
nitrogen, therefore, even before the war^ had become a number of 
organic products, such as tankage, fish scrap, and cottonseed meal, 
produced in this country, and guano imported from almost depleted 
deposits off the Pacific coast of South America. But with the coming 
of war other demands have been put upon most of these products, 
raising their price. In regard to cottonseed meal in particular, it 
has gradually become apparent that it is indirect and wasteful to add 
this material to soil to increase food production when it can be fed 
directly to cattle to accomplish more effectively the same purpose 
and then be later recovered in almost its entirety for fertilizing use 
in the form of manure. It would seem, therefore, that opposing 
economic demands are gradually withdrawing organic nitrogen of 
the kinds enumerated from the fertilizer industry. 
The third major source of nitrogen, as yet only partly developed, 
is coal. The nitrogen in coal might be termed fossilized nitrogen in 
that it represents a portion of the nitrogen of the atmosphere with- 
drawn in ages past by coal-forming plants and now fixed in the re- 
sultant coal to the extent on the average of over 20 pounds of nitro- 
gen to each ton of coal. When the coal is burned this nitrogen is 
given back to the atmosphere and lost. If the nitrogen were recov- 
ered from all the coal consumed throughout the world, the supply 
would more than suffice the total needs of industry during the era 
of extensive coal utilization, which is limited, however, to a short 
period of centuries. 
But recovery of nitrogen from all the coal used is an impracticable 
thing under present usage. In this country in 1913 we saved the 
nitrogen from only 3 per cent of the coal mined. That figure was 
perhaps as high as economic conditions permitted at that time; it 
is a little greater to-day, and it is subject to considerable increase in 
the future, provided the whole fabric of coal by-product develop- 
ment advances without dismemberment. This will be clearer if we 
consider that coal at present serves two prime functions — it furnishes 
fuel to produce heat and power and it supplies the coke required 
in the process of changing iron ores into metallic iron. 1 Roughly, 
12 per cent of the coal mined in the United States in 1913 was made 
into coke; that is, 69,000,000 tons of coal was so treated. Of this 
quantity, nitrogen was recovered from only a quarter, yet that nitro- 
gen supplied a significant part of our total needs. 
Coke is coal freed of certain liquids and gases which are given off 
when the coal is heated without access of air. The coke industry 
grew up many decades ago around Pittsburgh, because of the occur- 
rence of suitable coal in that locality, establishing there our great 
1 A minor use of coal is for the manufacture of illuminating gas, but nitrogen 
is recovered from a relatively low percentage of coal used for that purpose. 
