STOKES, George Gabriel On the Effect of the Internal Friction of Fluids on the Motion of Pendulums.
Cambridge: John W. Parker, 1850/1851. First edition.

Rare offprint of “one of his most important papers on hydrodynamics” (Parkinson in D.S.B.). In this paper Stokes introduced the notion of a Reynolds number and derived the fundamental law, named after him, for the drag force on small spherical objects (Encyclopedia Brittanica, Stokes’ Law). “Stokes applied his theory of the internal friction of fluids to the behavior of pendulums. Poisson, Challis. Green, and Plana had analyzed in the 1830’s the behavior of spheres oscillating in fluids, but Stokes took into account the effects of internal friction, including both spherical bobs and cylindrical pendulums. He then compared his theoretical calculations with the results of experiments conducted by others, including Coulomb, Bessel, and Baily. In the same paper he showed that the behavior of water droplets in the atmosphere depended almost completely on the internal friction of air and so explained how clouds could form in the atmosphere of the earth. On account of his theoretical analysis and experimental observations of pendulums combined with his study of gravity at the surface of the earth, Stokes became the foremost British authority on the principles of geodesy.” (D.S.B. XIII:75).

Large 4to: 286 x 225 mm. Offprint from: Transactions of the Cambridge Philosophical Society, Vol. IX, Part II. Pp. (2:blank), (2:title), 99, (1:blank). Contemporary plain wrappers (upper wrapper detached and chipped at edges, spine covering mostly worn away), unopened, internally very good.