William Thomson, 1st Baron Kelvin

The beauty and clearness of the dynamical theory, which asserts heat and light to be modes of motion, is at present obscured by two clouds.

Now I think hydrodynamics is to be the root of all physical science, and is at present second to none in the beauty of its mathematics.

Every boy... should be able by the age of 12 to write his own language with accuracy and some elegance; he should have a reading knowledge of French, and be able to translate Latin and easy Greek authors, and have some acquaintance with …

To live among friends is the primary essential of happiness.

Tesla has contributed more to electrical science than any man up to his time.

I need scarcely say that the beginning and maintenance of life on earth is absolutely and infinitely beyond the range of sound speculation in dynamical science.

Do not imagine that mathematics is hard and crabbed, and repulsive to common sense. It is merely the etherealization of common sense.

Mathematics is the only true metaphysics.

Symmetrical equations are good in their place, but 'vector' is a useless survival, or offshoot from quaternions, and has never been of the slightest use to any creature.

I am afraid I am not in the flight for “aerial navigation”. I was greatly interested in your work with kites; but I have not the smallest molecule of faith in aerial navigation other than ballooning or of expectation of good results from …

Quaternions came from Hamilton after his really good work had been done, and though beautifully ingenious, have been an unmixed evil to those who have touched them in any way.

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and …