22 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 1 



The paper was illustrated by lantern slides, and was discussed by 

 Messrs. Burka, Foote, Sosman, McKeehan, White, Stimson, Mer- 

 wiN, KIanolt, and WennER. 



Informal presentations: At the request of Mr. C. A. Briggs, Mr. 

 W. J. Humphreys spoke briefly concerning the aurora of March 22, 



1920. 

 Mr. G. F. Hull described an unusual aurora which he had witnessed. 



834th meeting 



The 834th meeting was held at the Cosmos Club April 10, 1920, with 

 50 persons present, and Vice-President Crittenden in the chair. 

 The program was as follows: 



H. C. Dickinson: Physical laboratory methods applied to aircraft 

 engines at high altitudes. 



A special laboratory equipped for making precise determinations of 

 the various factors in the performance of aircraft engines under all con- 

 ditions of operation was developed at the Bureau of Standards during 

 the war. The methods of measuring power, heat and temperature 

 distribution, pressure, densities, etc., are distinctly those of the physical 

 laboratory. In addition to studies of engine performance, parallel 

 investigations have been made of the problems of ignition, carburetion, 

 cooling, lubrication, etc., for which special laboratory equipment has 

 been provided. 



In connection with these researches, a number of special instruments 

 have been designed. These include a balanced-diaphragm pressure 

 indicator for recording engine cylinder pressures accurately by a point 

 to point method; an instrument for measuring the clearance volume in 

 engine cylinders ; and a device for measuring conveniently the maximum 

 cylinder pressure. 



The paper was illustrated by lantern slides, and was discussed by Mr. 

 Buckingham. 



M. D. Hersey: Old and new problems of aeronautic instruments. 



The speaker called attention to charts and instruments which had 

 accumulated on this subject since the occasion of his last paper before 

 the Society, which was the year before the war. 



The charts were as follows : 



1. Rejection limits for aviation altimeters. 



2. Temperature lag of aneroids. 



3. The two temperature effects on instruments with elastic action. 



4. Theory of groimd speed indicator. 



5. Results of Venturi tube experiments in air and water. 



6. Results of Venturi tube experiments in vacuum wind tunnel and on an airplane. 



7. Dimensional theory of compass damping. 



8. List of new problems awaiting solution as follows: 



(a) Stabilizer for ground speed indicators. 



(b) Air speed indicator for dirigibles. 



(c) True altitude meter. 



(d) Gyroscopic or double pivot compass. 



(e) Temperature compensated diaphragms with small elastic lag. 



