How could the thin upper crust of the earth--the mere rind three inches thick--be expected to yield crop after crop for a hundred years?
Deep ploughing could only be done by steam: now how many farmers possessed or used steam-ploughs?
Why, there were whole districts where such a thing was unknown.

They had neglected to manure the soil; to restore to it the chemical constituents of the crops.

But to speak upon artificial manure was enough to drive any man who had the power of thought into temporary insanity.

It was so utterly dispiriting to see men positively turning away from the means of obtaining good crops, and then crying out that they were ruined.

With drains, steam-ploughs, and artificial manure, a farmer might defy the weather.
Of course, continued the professor, it was assumed that the farmer had good substantial buildings and sufficient capital.