This scan of page 268 from Astronomy shows the clearest visual data available on Mars in 1935. Top: drawings of the Martian "canali" by Percival Lowell. Middle: seasonal changes on the planet's surface observed from May 10 to July 19, highlighting the alleged vegetation patches. Bottom: spectrograph comparisons of Mars and the Moon, used to make measurements of Mars' atmospheric composition.

Astronomy, John Charles Duncan. Harper & Brothers Publishers, New York/London, 1935