[Herschel and Humboldt] stirred up in me a burning zeal to add even the most humble contribution to the noble structure of Natural Science. No one or a dozen other books influenced me nearly so much as these two. I copied out from Humboldt long passages about Teneriffe and read them aloud on one of [my walking excursions].

One hand has surely worked throughout the universe.

The instruction at Edinburgh was altogether by lectures, and these were intolerably dull, with the exception of those on chemistry.

It's an awful stretcher to believe that a peacock's tail was thus formed but ... most people just don't get it - I must be a very bad explainer

It is not the most intellectual of the species that survives; it is not the strongest that survives; but the species that survives is the one that is able best to adapt and adjust to the changing environment in which it finds itself.

So great is the economy of nature, that most flowers which are fertilised by crepuscular or nocturnal insects emit their odour chiefly or exclusively in the evening.

The moral faculties are generally esteemed, and with justice, as of higher value than the intellectual powers. But we should always bear in mind that the activity of the mind in vividly recalling past impressions is one of the fundamental though secondary bases of conscience. This fact affords the strongest argument for educating and stimulating in all possible ways the intellectual faculties of every human being.