I can never satisfy myself until I can make a mechanical model of a thing. If I can make a mechanical model, I can understand it. As long as I cannot make a mechanical model all the way through I cannot understand.

Vortices of pure energy can exist and, if my theories are right, can compose the bodily form of an intelligent species.

Science is bound, by the everlasting vow of honour, to face fearlessly every problem which can be fairly presented to it.

Nothing can be more fatal to progress than a too confident reliance on mathematical symbols; for the student is only too apt to take the easier course, and consider the formula not the fact as the physical reality.

Questions of personal priority, however interesting they may be to the persons concerned, sink into insignificance in the prospect of any gain of deeper insight into the secrets of nature.

The only census of the senses, so far as I am aware, that ever before made them more than five, was the Irishman's reckoning of seven senses. I presume the Irishman's seventh sense was common sense; and I believe that the possession of that virtue by my countrymen-I speak as an Irishman.

[Referring to Fourier's mathematical theory of the conduction of heat] ... Fourier's great mathematical poem.