Gold and iron at the present day, as in ancient times, are the rulers of the world; and the great events in the world of mineral art are not the discovery of new substances, but of new and rich localities of old ones.

There is a mask of theory over the whole face of nature.

The person who did most to give to analysis the generality and symmetry which are now its pride, was also the person who made mechanics analytical; I mean Euler.

The object of science is knowledge; the objects of art are works. In art, truth is the means to an end; in science, it is the only end. Hence the practical arts are not to be classed among the sciences

We cannot observe external things without some degree of Thought; nor can we reflect upon our Thoughts, without being influenced in the course of our reflection by the Things which we have observed.

The catastrophist constructs theories, the uniformitarian demolishes them.

The hypotheses we accept ought to explain phenomena which we have observed. But they ought to do more than this: our hypotheses ought to foretell phenomena which have not yet been observed.