Twoof the most enthusiastic advocates of the compressed air engine for use in model aëroplanes are Messrs. Frank Schober and RudolphFunk, both members of the Aëro Science Club. For a number of months both these gentlemen have experimented with compressed air engines of various designs, until they finally produced what is perhaps one of the most satisfactory rotary engines now in use, from a standpoint of simplicity and results.