598 TEE POPULAR SCIENCE MONTHLY 



out. But whatever the logic of the question, it would and should make 

 very little impression on the average healthy-minded individual. Our 

 problem presents a very similar situation in which we may justly ques- 

 tion whether a healthy-minded person should have any fear about the 

 exhaustion of the proper number of food units that may be required, 

 even if he is as far sighted as a conservation congress. 



Soon after Malthus had written his book, his theory fell into dis- 

 repute because of the opening of the great interior plain of the United 

 States. But thinkers soon saw that the principle was just as true as 

 before, though the pressure of conditions was temporarily postponed. 

 But now that we have come practically to the end of free land we seem 

 to be nearer than ever to the threshold of the catastrophe. Even such 

 a good thinker as Joseph L. Lee, the Boston philanthropist, feels it, for 

 in speaking about immigration he says : 



America is not infinitely large. It will in any case — in what, compared with 

 the long future, must be regarded as a very short time — become so crowded that 

 any further increase of the population — except at a comparatively slow rate can 

 be made only at the cost of lowering the general standard of prosperity. 



Land, however, is only one of the three factors in production. The 

 incalculable additions to labor and capital in the last generation are so 

 much greater contributions than more land could be that we are getting 

 farther and farther away from, rather than nearer to, the catastrophe. 

 To return to the analogy of the sun's heat : it is of course true that the 

 sun can not continue to give off heat forever and remain as hot as 

 before. But we have an interesting condition arising from the fact that 

 though the sun is radiating its heat and thus diminishing its potential 

 energy, yet the process of contraction which is taking place within the 

 sun causes it to generate heat as rapidly as it is losing it, and while this 

 is not a perpetual-motion machine, for the purposes of giving continu- 

 ity of heat to the earth it is a perfectly satisfactory arrangement. 



In like manner it makes no difference whether we get more land, or 

 more productivity from the same land. Malthus found that population 

 tended to multiply by geometrical progression, while the means of 

 subsistence multiplied by arithmetical progression. This is true so 

 long as the process is on an " equal dose " basis. But the conspicuous 

 fact of modern times is that means of subsistence are multiplying at a 

 rate which makes the multiplication of population look like the pace of 

 the historic tortoise compared to that of Achilles, whom logic tried to 

 keep from catching up. The logic of the law of diminishing returns is 

 of the same type. Professor Carver shows that on a certain area of 

 land twenty men can produce more per man than fifty, though the 

 total production of the twenty men is but 380 bushels compared with 

 650 bushels produced by the fifty men. As a matter of fact, in spite of 

 Zeno's logic we know that Achilles could overtake the tortoise, and we 



