I was at first almost frightened when I saw such mathematical force made to bear upon the subject, and then wondered to see that the subject stood it so well.

Letter to James Clerk Maxwell (25 March 1857), commenting on Maxwell's paper titled "On Faraday's Lines of Force"; letter published in The Life of James Clerk Maxwell: With Selections from His Correspondence (1884), edited by Lewis Campbell and William Garnett, p. 200; also in Coming of Age in the Milky Way (2003) by Timothy Ferris, p. 186