PKESIDENt's address. — SECTION G. 



193 



The graph of these relative results — graph No. 2 — appears as 

 a zig-zag line, the general trend of which is a curve convex up- 

 wards, that is, the rate of increase becomes less and less,* or, in 

 other words, the difficulty of increasing the quantity of produc- 

 tion • augments as time goes on. 



It is, of course, true that the yield may be increased in the 

 case of individual crops; that of beet sugar in Europe is a classic 

 example. If quinquennial means be formed of the yield in tons 

 of cane sugar per acre in Queensland, it will be seen that the 



Graph No. 3. 



graph of the general trend — graph No. 2 — is a curve concave up- 

 wards with the following values approximately t : — 



A wider study of agricultural yields shows, however, that on 

 the whole the use of fertilizers is rather to maintain production 



• The curve is very nearly expressed by — 



N = 1 + 0-04 (Y - 1898)' - 0' 00083 (Y - 1898)S 

 ■where N is the annual total relative to that of 1898, and Y is the date year. 



t The results for individual years, of course, vary somewhat from these. See the dots on 

 the graph No. 2. 



