PHENOMENA OF ORGANIC NATURE 



437 



any more than a mathematician does when he ex- 

 pounds his problem. If you show that the con- 

 ditions of your problem are such as may actually 

 occur in Nature and do not transgress any of the 

 known laws of Nature in working out your pro- 

 position, then you are as safe in the conclusion 

 you arrive at as is the mathematician in arriving 

 at the solution of his problem. In science, the 

 only way of getting rid of the complications with 

 which a subject of this kind is environed, is to 

 work in this deductive method. What will be 

 the result, then ? I will suppose that every plant 

 requires one square foot of ground to live upon ; 

 and the result will be that, in the course of nine 

 years, the plant will have occupied every single 

 available spot in the whole globe ! I have chalked 

 upon the blackboard the figures by which I arrive 

 at the result : 



51,000,000 square miles the^i 



dry surface of the earth x I ,.. , . on ^ no . nn -._ nnn 



27;878,400-the number of f=s<l-ft. 1.421,, 98,400,000, 00 



sq. ft. in 1 sq. mile 



being 531,326,600,000,000 



square feet less than would be required at the end of the ninth 

 year. 



