Note that the forty horse-power cylinder motor weighs one hundred seventy-five pounds and gives a thrust of three hundred ten pounds when equipped with a seven foot diameter by six foot pitch propeller turning at nine hundred revolutions per minute. The pitch speed of the propeller at this rate is in excess of a mile a minute. Gas-Consumption: The consumption of gas is three-fourths pint per horse-power per hour. The engine can be throttled and consumption reduced in nearly direct ratio to the horse-power developed. Consumption on full throttle per hour is seven and one-fourth gallons gasoline and one gallon of oil. The oil capacity of the small pan is four gallons; of the large pan, six gallons. Testing and Power: Each engine is given an extended run with propeller load. After giving the required standing thrust at the proper speed, the engine is completely torn down for inspection and carbon removed. After assembling, it is given a second test on a water dynamometer, which gives the horse-power developed. Miscellaneous: Few people realise that the aeronautical motor is subjected to usage equalled by few internal combustion engines. The average car engine is seldom run on full throttle for extended periods. The marine engine is ordinarily a very heavy, slow speed machine. The aeronautical motor, to run at the high speeds under full load demanded to-day, must of necessity be designed with this fact in mind, and particular attention paid to numerous weaknesses apt to develop under this treatment. Adding to the above the necessity for minimum weight while still retaining a sufficient factor of safety in all parts, it is evident that an aeronautical motor must be designed as such and not be a modified edition of an automobile engine with a few pounds removed here and there. PARTS OF CURTISS MOTOR–A COMPLETE LIST. 1-5, Breather Pipe Cap Screw & Flange, Collar, Cap & Clip; 6, Ball Bearing (Radial); 7-8, Crank Case, Upper Half & Lower Half; 9-10, Crank Case Bolt, Small & Large; 11, Crank Shaft. 12, Cam Shaft; 13-15, Cam Shaft Bearing, Front, Centre, & Rear; 16, Cam Shaft Bearing Sleeve, Rear; 17-18, Cam Shaft Gear & Retaining Screw; 19-20, Cam Shaft Bearing Clamping Screw, Centre, & Retaining Screw; 21, Cam Follower Guide Stud; 22, Cam Follower Guide Screw; 23, Cam Follower; 24-25, Cam Follower Guide & Plug. 26, Cylinder; 27, Cylinder Tie Down Yoke; 28-29, Cylinder Stud, Long & Short; 30, Cylinder Stud Nut; 31-32, Connecting Rod & Bolt; 33, Connecting Rod Bolt Nut; 34, Compression Tee for Oil Pipe; 35, Compression Coupling Sleeve; 36-37, Cable Holder & Screw; 38-39, Cable Tube & End; 40-41, Cable Tube Clip & Screw; 42, Carburetor Water Pipe Clip.