Magnetic observations on board HMS Bloodhound, by [Edward John Johnson ?] Magnetic observations and compass deviations observed aboard HMS Bloodhound at Greenhithe, on the Thames Estuary, England. This material is related to the manuscript paper AP/30/7, published in abstract as 'Magnetical experiments on board H.M. Iron Steam Vessel ‘Bloodhound’ ', by Captain Edward Johnson, R.N., F.R.S', Abstracts of the papers communicated to the Royal Society, v.5 (1851), pp.727-728. The paper notes that: 'These experiments were undertaken with the view of ascertaining whether the action of steam upon the hull of an iron vessel affects a compass, properly placed, in any degree that may be of practical importance in its navigation; and also whether the keeling of the vessel produces any alteration in the deviations, or disturbs a compass so placed to any considerable extent...' 6-11 May 1847