To assist his new hobby, Lowell bought himself equipment: an observatory built from scratch in Flagstaff, Arizona.
He soon released a trilogy of studies: Mars (1895); Mars and its Canals (1906); and Mars as the Abode of Life (1908). His thesis? Simple: Schiaparelli’s canals were actually the irrigation channels of an advanced civilization that funneled water from its polar caps in accordance with seasonal demand and a changing climate. Weirder still, the Martian canals were not able to be reliably observed (William Henry Pickering, one of the assistants in Flagstaff, could not see the channels, despite looking through the same equipment where they materialized for Lowell and Andrew Ellicott Douglass). There is some evidence that the whole affair was a collective hallucination, arising from an error built into human pattern recognition. — via Alien Aqueducts: The Maps of Martian Canals – The Public Domain Review