July 18 – Total solar eclipse. Warren De La Rue's photographs of this event, taken in Spain, together with those of Angelo Secchi, demonstrate the solar character of the prominences or red flames seen around the limb of the Moon during such an eclipse.[1]
John Curtis publishes Farm Insects, being the natural history and economy of the insects injurious to the field crops of Great Britain and Ireland... with suggestions for their destruction in Glasgow.
Joseph Dalton Hooker concludes publication of The Botany of the Antarctic Voyage of H.M. Discovery Ships Erebus and Terror ... 1839–1843 with issue of the final part of Flora Tasmaniae in London.[2]
Stanislao Cannizzaro, resurrecting Avogadro's ideas regarding diatomic molecules, compiles a table of atomic weights and presents it at the 1860 Karlsruhe Congress, ending decades of conflicting atomic weights and molecular formulas, and leading to Mendeleev's discovery of the periodic law.[4]
Edward Samuel Ritchie, considered to be the most innovative instrument maker in nineteenth-century America, receives a U.S. patent for the first successful and practicable liquid-filled marine compass suitable for general use.