Copy letter, from Sir John Herschel to Jacques Babinet, dated at Collingwood Copy of a letter. Jacques Babinet's solution to torsion thread arrangement is simpler and more ingenious than John Frederick William Herschel's. Enquires about details of gravimetric balance. Pendulum measurements. Density of continents. Clarification of John Frederick William Herschel's privileges as foreign associate of Institute. Death of J. B. Biot. 24 February 1862