Mathematics may be compared to a mill of exquisite workmanship, which grinds you stuff of any degree of fineness; but, nevertheless, what you get out depends upon what you put in; and as the grandest mill in the world will not extract wheat-flour from peascod, so pages of formulae will not get a definite result out of loose data.

"Geological Reform", Quarterly Journal of the Geological Society of London, Vol. 25 (1869); as reprinted in Huxley, Discourses, Biological and Geological essays (1909), pp. 335–336.