First LawIn every animal which has not passed the limit of its development, a more frequent and continuous use of any organ gradually strengthens, develops and enlarges that organ, and gives it a power proportional...

The great age of the earth will appear greater to man when he understands the origin of living organisms and the reasons for the gradual development and improvement of their organization. This antiquity will appear...

It is not the organs—that is, the character and form of the animal’s bodily parts—that have given rise to its habits and particular structures. It is the habits and manner of life and the conditions...

It is not always the magnitude of the differences observed between species that must determine specific distinctions, but the constant preservation of those differences in reproduction.

It is not enough to discover and prove a useful truth previously unknown, but that it is necessary also to be able to propagate it and get it recognized.

A sound Physics of the Earth should include all the primary considerations of the earth’s atmosphere, of the characteristics and continual changes of the earth’s external crust, and finally of the origin and development of...