favour". Now, I will ask you to imagine further that it shall be a
plant which shall produce every year fifty seeds, which is a very
moderate number for a plant to produce; and that, by the action of the
winds and currents, these seeds shall be equally and gradually
distributed over the whole surface of the land. I want you now to
trace out what will occur, and you will observe that I am not talking
fallaciously any more than a mathematician does when he expounds his
problem. If you show that the conditions 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 proposition, 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:-

Plants. Plants
1 x 50 in 1st year = 50
50 x 50 " 2nd " = 2,500
2,500 x 50 " 3rd " = 125,000
125,000 x 50 " 4th " = 6,250,000
6,250,000 x 50 " 5th " = 312,500,000
312,500,000 x 50 " 6th " = 15,625,000,000
15,625,000,000 x 50 " 7th " = 781,250,000,000
781,250,000,000 x 50 " 8th " = 39,062,500,000,000
39,062,500,000,000 x 50& " 9th " = 1,953,125,000,000,000