Letter from John Henry Lefroy, Longwood to [James Clark] Ross Lefroy sends Ross results of observations made at six different stations as requested by Ross. Includes results when poles direct, poles reversed and the means. Brief description of Lefroy’s method of observation. Lefroy suggests making a complete set of [observations] in ‘different azimuths’. Updates on the work of the observatory at [Longwood]. 17 February 1840