42 BULLETIN 2, U. S. DEPAKTMENT OF AGKICULTUKE. 
A word of warning, however, should be given those operators 
whose crews take menhaden in the late fall and the winter, that if 
they catch spawning fish they are running the risk of decreasing the 
supply. Serious interference with the fish at their spawning season 
means the inevitable depletion of the schools. 
IN THE LIGHT OF THE FUTURE DEMAND FOR NITROGEN. 
Certainly it is true that there will continue to be a use for nitrogen 
compounds for fertilizers for many years to come, and that for a 
time, at least, this use will be a rapidly increasing one. Whether 
there always will be such a demand is impossible to say and idle to 
speculate. The understanding of fertilizers and their action in the 
stimulation of plant growth now is only in its incipiency. Subse- 
quent investigation may show, and doubtless will, that some of our 
agricultural practices are based on misconceptions. Subsequent in- 
vestigations may show that certain of the materials now used as fer- 
tilizers are not as good as certain others yet to be tested, for it is 
known definitely that many other substances besides compounds of 
nitrogen, potassium, and phosphorous produce a stimulation similar, 
or, at least, analogous, to that produced by the present ingredients of 
commercial fertilizers regarded as essential. 
The general scarcity of nitrogenous compounds has stimulated the 
investigation of processes for " fixing " the nitrogen of the atmos- 
phere so that to-day there are at least three distinct methods of 
bringing about reaction between nitrogen and other substances which 
have been made the base of nitrogen-fixing industries. These are 
methods for oxidizing the nitrogen of air to nitric acid, for bringing 
about a union between the nitrogen of air and calcium carbide to form 
calcium cyanamide, and for inducing a reaction between the nitrogen 
of air and hydrogen to form ammonia. These industries are only in 
their infancy, so to speak, having been in operation only a few years. 
The rapid development of and improvement in the processes, growth 
in number and size of plants, and corresponding increase in output 
show that already they are on a satisfactory commercial basis and be- 
speak for them a successful future. Whether they will find it com- 
mercially advantageous or possible to market nitrogenous compounds 
at a lower price than now obtains or at a price with which the manu- 
facturers of fish scrap can not compete remains for the future to dis- 
close. With an unlimited and easily accessible supply of 'raw mate- 
rials and a practically inexhaustible source of power for operation 
