Francis Ronalds and Charles Brooke independently invented magnetographs in 1846 that continuously recorded the magnet's movements using photography, thus easing the load on observers.
Francis Ronalds ja Charles Brooke leiutasid kumbki iseseisvalt magnetograafi 1846. aastal, mis salvestas magnetite liikumist fotograafia abil ning seeläbi kergendas vaatlejate tööd.