Note 43 — DEVELOPMENT OF GRAVITY PENDULUMS IN THE 19th CENTURY
Reading edition
C. A. F. Peters, Briefwechsel zwischen C. F. Gauss und H. C. Schumacher (Altona, Germany, 1860), Band 2, p. 3. The correction required if the times of swing are not exactly the same is said to have been given also by Bohnenberger.