Lettre autographe signée, adressée au Pr Foerster. Cambridge, 6 février 1870 ; 4 pages in-8°. « Meantime you have probably before now received my memoire on the transatlantic longitude, which, though finished soon after my return home three years ago, was not published by the new super-intendent of the Coast Survey ; but has been independently printed vy the Smithsonian Institution. [ ] Bruhuss memoir of Encke reached me a few weeks ago, and I have been reading it with a good deal of pleasure [ ] circumstances have placed it in my power to undertake an astronomical expedition to the Southern Hemisphere [ ] with the view of founding a permanent observatory & of completing the zone-catalogue [ ] May I ask of your kindness information as to the clocks now made by Tiede [ ] what form of chronograph is most in use [ ] in Germany. » Rare.
