Nests, young, food, habits, and enemies of the voles of the genus Phenacomys.

"Aerodynamic tests were made with four geometrically similar metal propellers of different diameters, on a Wright "Whirlwind" J-5 engine in an open cockpit fuselage. The results show little difference in the characteristics of the various propellers, the only one of any importance being an increase of efficiency of the order of 1 per cent for a 5 per cent increase of diameter, within the range of the tests" (p. 107).

From Summary: "The trials reported in this report were instigated by the Bureau of Aeronautics of the Navy Department for the purpose of determining accurately the speed and resistance of the U. S. S. "Los Angeles" with and without water recovery apparatus, and to clear up the apparent discrepancies between the speed attained in service and in the original trials in Germany. The trials proved very conclusively that the water recovery apparatus increases the resistance about 20 per cent, which is serious, and shows the importance of developing a type of recovery having less resistance. Between the American and the German speed trials without water recovery there remains an unexplained discrepancy of nearly 6 per cent in speed at a given rate of engine revolutions."

The National Bureau of Standards tested a 300-horsepower Hispano-Suiza engine to determine the characteristic performance of the engine at various altitudes. The engine was operated at the ground, at 25,000 feet, and at intermediate altitudes, both at full loads similar to those that would be imposed upon the engine at various speeds by a propeller whose normal full-load speed was 1,800 r.p.m. Friction horsepower also was determined in order that the mechanical efficiency of the engine might be calculated.