“[T]he production of heat alone is not sufficient to give birth to the impelling power: it is necessary that there should also be cold; without it, the heat would be useless.”

p, 125
Reflections on the Motive Power of Heat (1824)

First Memoir.
The Mechanical Theory of Heat (1867)

Source: The Education of the Will (1920), p. 100

Source: Don Quixote de la Mancha (1605–1615), Part II (1615), Book III, Ch. 6.

Light (1919), Ch. XXII - Light

This being the case, it is evident that the onus probandi [burden of proof] ought to lie with those who are willing to establish such an hypothesis, for it does not appear that Nature is in the habit of using one and the same mechanism with any two of our senses. Witness the vibration of air that makes sound, the effluvia that occasion smells, the particles that produce taste, the resistance or repulsive powers that affect the touch—all these are evidently suited to their respective organs of sense.
Source: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" on his discovery of the infrared.

"Points of Character", p. 37.
Faraday as a Discoverer (1868)
Context: A point highly illustrative of the character of Faraday now comes into view. He gave an account of his discovery of Magneto-electricity in a letter to his friend M. Hachette, of Paris, who communicated the letter to the Academy of Sciences. The letter was translated and published; and immediately afterwards two distinguished Italian philosophers took up the subject, made numerous experiments, and published their results before the complete memoirs of Faraday had met the public eye. This evidently irritated him. He reprinted the paper of the learned Italians in the Philosophical Magazine accompanied by sharp critical notes from himself. He also wrote a letter dated Dec. 1,1832, to Gay Lussac, who was then one of the editors of the Annales de Chimie in which he analysed the results of the Italian philosophers, pointing out their errors, and' defending himself from what he regarded as imputations on his character. The style of this letter is unexceptionable, for Faraday could not write otherwise than as a gentleman; but the letter shows that had he willed it he could have hit hard. We have heard much of Faraday's gentleness and sweetness and tenderness. It is all true, but it is very incomplete. You cannot resolve a powerful nature into these elements, and Faraday's character would have been less admirable than it was had it not embraced forces and tendencies to which the silky adjectives "gentle" and "tender" would by no means apply. Underneath his sweetness and gentleness was the heat of a volcano. He was a man of excitable and fiery nature; but through high self-discipline he had converted the fire into a central glow and motive power of life, instead of permitting it to waste itself in useless passion. "He that is slow to anger" saith the sage, "is greater than the mighty, and he that ruleth his own spirit than he that taketh a city." Faraday was not slow to anger, but he completely ruled his own spirit, and thus, though he took no cities, he captivated all hearts.

Source: Journey Beyond Tomorrow (1962), Chapter 6 “Joenes and the Three #505justice Truck Drivers” (pp. 44-45)

Source: Human, All Too Human