592 THE POPULAR SCIENCE MONTHLY 



and of natural disease. Practically, however, this would be of little 

 difference; the leather made from the hides of animals dead of old age 

 would be of so low value as to be almost worthless; and the use of the 

 hides of animals dead of disease, many forms of which are infectious 

 and communicable to man, would be fraught with danger and difficult 

 of execution. Mankind would have to face the problem of clothing 

 without the aid of leather and fur. 



Can the surface of the earth (for the fishes of the sea would have 

 to be excluded) raise enough grain, fruits, nuts and vegetables, added 

 to dairy products, to meet the albumin needs of the present earth's 

 population? Unhesitatingly it may be stated that the area of the 

 earth's surface now under cultivation could not, with the present meth- 

 ods of agriculture, dependably produce enough plant albumin to meet 

 the needs of the present population. Very large areas of the earth's 

 surface at present produce only grasses, shrubs and trees. Man can 

 neither graze nor browse. At present these plants are consumed by 

 cattle, goats, sheep and swine, whose albumin is utilized in turn by man. 

 It is through the mediation of these animals that the vegetation 

 of enormous areas of land is made available for mankind. At present 

 probably one half of the albumin needs of mankind are met by animal 

 albumin. To meet these needs with plant albumin and dairy products 

 the world's production of grains and legumins would need to be doubled 

 at the least. It is quite certain that this could not, with the uttermost 

 efforts of the world's population, be dependably accomplished at present. 

 It is possible that it might be accomplished, with the present methods 

 on the present acreage of tillable soil, if no untoward manifestations of 

 the elements occurred (such as severe winters, unseasonable frosts, 

 floods, droughts, storms, excessive heat), with a dependable rain-fall in 

 both time and space. But mankind would be yearly at the mercy of 

 the elements. To meet fully and safely the needs of the growing popu- 

 lation, four scientific advances of monumental magnitude would need 

 to be attained. 



The methods of the cultivation of the soil must be so intensified and 

 revolutionized through scientific investigations as to make the yield of 

 the soil less disproportional to its potential. 



The conservation of water must be accomplished on a scale never 

 before dreamed of. 



The world-wide ravages of the parasitic diseases of plants must be 

 checked. 



The conversion of inert atmospheric nitrogen into potential soil 

 nitrogen must be accomplished upon a vast scale through microbic and 

 electro-chemical agencies. 



The results of the accomplishment of these four advances, judged 

 merely from present scientific knowledge of the possibilities in the four 



