October 24, 1919] 



SCIENCE 



387 



CYRIL G. HOPKINS 



Dr. Cyril G. Hopkins, head of the depart- 

 ment of agronomy of the University of Illi- 

 nois, passed away at the British Military Hos- 

 pital at Gibraltar, on October 6, of congestion 

 of the brain with malarial complications. 



He had finished a year's work in the study 

 of the exhausted soils of Greece under the aus- 

 pices of the American Red Cross, had made 

 his official report, had seen to the preparation 

 of a Greek translation, had been decorated by 

 the King of Greece " for distinguished serv- 

 ice," and had taken ship for home when, with- 

 out warning, the third day out from Gibraltar, 

 the fatal illness struck him and at the age of 

 fifty-three at the very zenith of his powers, his 

 service was brought to an end. Just what that 

 service was, I shall attempt to state as clearly 

 as it is possible for a layman to state it. 



Dr. Hopkins was a chemist both by training 

 and by instinct. He had the chemist's concep- 

 tion that everything about us is built up of 

 well-known elements in varying but definite 

 proportions. He carried this conception into 

 crops and into the study of soils which pro- 

 vides certain of the necessary elements in 

 crop production. He was keenV" impressed 

 with the fact that most crops are i)roduced 

 out of the natural store of plant food just as 

 coal is produced from the mines without restor- 

 ation, and that this being the case, the indi- 

 vidual can not compete against an agriculture 

 which mostly draws upon virgin stores if he 

 undertakes to apply to his land anything more 

 than what is necessary to increase the 

 amount " of the limiting element." By 

 this, he meant the particular form of plant 

 food which chances to be lacking and, there- 

 fore, which limited the combinations which 

 might be made in the form of plants. He 

 announced the doctrine that the farmer 

 should first know his soil by an inventory of 

 its constituents, particularly those likely to 

 run short as a merchant takes frequent inven- 

 tory of his stock and places timely orders 

 where the stock is running short, leaving the 

 full shelves alone until they shall begin to run 

 low. 



"With this view of the situation, he made 



scientific objections to the w'hole theory of 

 prepared mixed fertilizers just as he did to the 

 idea of a patent medicine, believing with the 

 physician that the first step is to diagnose the 

 situation and then to find the particular rem- 

 edy that is needed and apply it. He particu- 

 larly objected to the use of " acid phosphates " 

 partly because of cost arising from the fact 

 that a full half of the weight consisted of sul- 

 phuric acid which is not a fertilizer and partly 

 because of the fact that the acidity of soils, 

 even under normal conditions needs frequent 

 correction in order that the bacteria may 

 thrive upon the roots of legumes and the store 

 of nitrogen be properly increased. 



Again with this conception of maintaining 

 fertility. Dr. Hopkins believed, and his experi- 

 ments seemed to confirm the belief, that suffi- 

 cient amounts of nitrogen for ordinary farm- 

 ing purposes could be obtained by proper ro- 

 tation of crops introducing the legumes with 

 reasonable frequency, provided that soils were 

 not allowed to become acid and that suitable 

 measures were taken to promote bacterial 

 growth. 



The great slogan which Dr. Hopkins con- 

 stantly emp'loyed was that of a "Permanent 

 Agriculture," by which he meant that in the 

 application of fertility, regard should be had, 

 not only for the immediate results, but for the 

 permanent effect upon the land, the test of 

 which lay in this question: "Am I applying 

 in my fertilizers as much phosphorus or po- 

 tassium as I am removing in my crops and am 

 I ahstracting from the atmosphere hy my ro- 

 tations enough nitrogen to restore the draft 

 upon the land? " He insisted that every 

 farmer should not only be able to answer this 

 question in the affirmative, but that if he chose 

 for application the cheapest sources of plant 

 food, he would be able to apply a little more 

 year by year than he took out. 



For this reason, the system which Dr. Hop- 

 kins advocated was the application of enough 

 fertilizer to replace what would be taken out 

 by a hundred bushels of corn, fifty bushels of 

 wheat and so on for the other maximum 

 yields. In this way, he argued — and seemed 

 fully able to prove — that the American farmer 



