In 1639, Horrocks was the only astronomer to realise that a transit of Venus was imminent; others became aware of it only after the event when Horrocks's report of it was circulated.
În 1639, Horrocks a fost singurul astronom care a realizat că un tranzit al lui Venus era iminent; ceilalți nu au luat cunoștință de eveniment decât după publicarea dării de seamă a observațiilor lui Horrocks.