It is notorious that the same discovery is frequently made simultaneously and quite independently, by different persons. Thus, to speak of only a few cases in late years, the discoveries of photography, of electric telegraphy, and of the planet Neptune through theoretical calculations, have all their rival claimants. It would seem, that discoveries are usually made when the time is ripe for them - that is to say, when the ideas from which they naturally flow are fermenting in the minds of many men.

Well-washed and well-combed domestic pets grow dull; they miss the stimulus of fleas.

It is always the case with the best work, that it is misrepresented, and disparaged at first, for it takes a curiously long time for new ideas to become current, and the older men who ought to be capable of taking them in freely, will not do so through prejudice.

I do not so easily think in words.... after being hard at work having arrived at results that are perfectly clear... I have to translate my thoughts in a language that does not run evenly with them.

The inferiority of photographs to the best works of artists, so far as resemblance is concerned, lies in their catching no more than a single expression. If many photographs of a person were taken at different times, perhaps even years apart, their composite would possess that in which a single photograph is deficient.

Life is a republic where the individuals are for the most part unconscious that while they are working for themselves they are also working for the public good.

The publication in 1859 of the Origin of Species by Charles Darwin made a marked epoch in my own mental development, as it did in that of human thought generally. Its effect was to demolish a multitude of dogmatic barriers by a single stroke, and to arouse a spirit of rebellion against all ancient authorities whose positive and unauthenticated statements were contradicted by modern science.