The most powerful factors in the world are clear ideas in the minds of energetic men of good will.

The chief end of science is to make things clear, the educative aim is to foster the inquisitive spirit.

There is no counting the unsolved problems of Natural History.

Was it not the great philosopher and mathematician Leibnitz who said that the more knowledge advances the more it becomes possible to condense it into little books?

The man who has grit enough to bring about the afforestation or the irrigation of a country is not less worthy of honor than its conqueror.

All Nature bristles with the marks of interrogation-among the grass and the petals of flowers, amidst the feathers of birds and the hairs of mammals, on mountain and moorland, in sea and sky-everywhere. It is one of the joys of life to discover those marks of interrogation, these unsolved and half-solved problems and try to answer their questions.