Copy letter, from Sir John Herschel to Henry Kater, dated at Paris Copy of letter, copied as part of the correspondence project led by Colonel John Herschel FRS following the death of his father. Delivered Royal Society [of London] resolution on 'Junction of French and English triangles' to François Arago. Arago alone will meet Henry Kater and T. F. Colby to finish triangles this summer. J. B. Biot will collaborate next year with Henry Kater on pendulum measurements. 5 August 1821