CAVENDISH, Henry. Experiments to determine the Density of the Earth.
London: Peter Elmsly, 1798. First edition.

His famous paper on the determination of the density of the earth (or weighing of the world), by means of John Michell’s torsion balance. “Henry Cavendish had fitful habits of publication that did not at all reveal the universal scope of his natural philosophy. He wrote no books and fewer than twenty articles in a career of nearly fifty years. Only one major paper was theoretical, a study of electricity in 1771; the remainder of his major papers were carefully delimited experimental inquiries, the most important of which were those on pneumatic chemistry in 1766 and 1783–1788, on freezing temperatures in 1783–1788, and on the density of the earth in 1798.” (D.S.B. III:155). “The apparatus consisted of two lead balls on either end of a suspended beam; these movable balls were attracted by a pair of stationary lead balls. Cavendish calculated the force of attraction between the balls from the observed period of oscillation of the balance and deduced the density of the earth from the force. He found it to be 5.48 times that of water. Cavendish was the first to observe gravitational motions induced by comparatively minute portions of ordinary matter. The attractions that he measured were unprecedentedly small, being only 1/500,000,000 times as great as the weight of the bodies. By weighing the world he rendered the law of gravitation complete. The law was no longer a proportionality statement but a quantitatively exact one; this was the most important addition to the science of gravitation since Newton.” (D.S.B III:158). Norman 422.

4to: Extracted from: Philosophical Transactions of the Royal Society of London, vol. 88, 1798, pp. 469-526 and 2 engraved folding plates. Recent plain blue wrappers. Some very light spotting, in all a fine copy.