| Warren De la Rue Sun Spots 1861, 24 September (taken) 1862, 9 May (published) Photogalvanograph Archive Farms The Patrick Montgomery Collection, Object No. 2019.544a LL/122092 Monthly Notices of the Royal Astronomical Society, London : Priestley and Weale, Vol. XXII, No 7, May 9, 1862
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