Letter, from Thomas Henderson to Sir John Herschel, dated at Edinburgh Autograph letter signed by sender. Has had a reply from Thomas Maclear stating that all work has ceased at the Cape Observatory until the work on calculating the Arc of the Meridian has finished. F. W. Bessel has expressed a wish that Centaure should be observed with a heliometer. Wishes a good heliometer could be sent to the Cape. 4 October 1842