 Francis Dickens' diary written during his charge at Fort Pitt, though very brief, is an important document of the events of the siege that led to the evacuation of the mounted police from the fort.On his website, David J. Carter describes the events at Fort Pitt.This site [Frog Lake, following Cree attacks on priests and Hudson's Bay Company employees and family members] was 35 miles northwest of Fort Pitt.