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THE SUBSTANCE OF AIR MADE VISIBLE BY PHOTOGRAPHY. 
The iphotograph ‘was taken by an eminent Japanese savant, M. Tanakadate, Professor of Physics in Tokio University. In 
order to obtain the effect, the air of a dark room has been heated with Bunsen burners and a propeller has been set rotating in 
front of the hot air. In this way eddies of hot and cold are produced, and these are illuminated with an electric flash and 
photographed. The propeller was fifty centimetres in diameter and mounted on a horizontal shaft 
