Draft letter, from Sir John Herschel to John James Waterston, dated at Collingwood Autographed draft letter, signed or initialed by sender, with annotations by Sir John Herschel. Not surprised that scientific journals decline simple mechanical explanation of heat based on principle of conservation of vis viva. Admits that it has advocates, but John Frederick William Herschel has no time to devote to it. [John Frederick William Herschel's annotation: Not sent. Waterston gave no address but 'London'.] 3 August 1846