While we are discussing horsepower, it might be well to find out just what we mean by the term. In connection with steam and gasoline engines it is used for the reason that the horse had for years been man’s most common power plant. One horsepower represents the power ascribed to a heavy dray horse in the days of horse-drawn vehicles. This “standard” one-horse’s-power includes the three factors, time, weight, and distance, or the length of time it takes to move a certain weight a certain distance. One horsepower in these factors amounts to the ability to lift 33,000 pounds one foot in one minute. Actual brake tests, where an experimental engine shows its ability to lift a certain number of pounds so high in one minute, gives the engineer a series of tables to be used in designing other engines. Each cylinder produces an equal share of the engine’s total horsepower. Thus each cylinder of the nine-cylinder, 200-horsepower, Wright radial engine produced slightly over 22 horsepower, or eight more than the entire four cylinders of the Wright Brothers’ 1903 engine. With the introduction of the first practical, light-weight, air-cooled, radial engine, American aviation underwent a great change for the better. The Lawrance-designed Wright J engines promptly began to put a long succession of famous fliers and famous airplanes in the books for one record after another. The Stout-designed Ford tri-motor transport plane was powered with Wright J3 radials. The J3 was adapted for use by the United States Navy and led the Navy to discontinue entirely its use of liquid-cooled power plants in favor of air-cooled radial engines for all its service airplanes. Wright J4 engines powered the flight of Admiral Richard E. Byrd and Floyd Bennett over the North Pole in 1926. Tony Fokker, who had designed Germany’s fighters in World War I, began to make records with his American-built planes powered with Wright radials. With the arrival of a suitable engine, fliers all over the country began to think of the Raymond Orteig prize of $25,000 for the first nonstop flight from New York to Paris. This offer had been standing since 1919. Admiral Byrd was ready to try for it when a slim, quiet, young air mail pilot hopped off from Long Island, N. Y. Flying a Ryan monoplane powered with a Wright J5 radial, this young fellow flew the Atlantic nonstop to land, some thirty-three hours and thirty-nine minutes later, in Paris with the quiet announcement, “I am Charles Lindbergh.” RECORD-MAKING FOKKER TRI-MOTOR TRANSPORT PLANE