Letter from Balfour Stewart, Kew Observatory to Edward Sabine Stewart informs Sabine they ‘have an old bifilar’ which will ‘serve’ as a declinometer for Dr Walker. Refers to the vertical force magnet. Includes a list of facts ‘in favour of the auroral theory’. Stewart remarks if Mr [Warren] de La Rue would be able to take a photograph ‘during an aurora’ to show ‘corresponding phenomena in the different planets’. Discussion regarding ‘the total magnetic action of the sun’. 1 September 1862