XO. 3 EUROPEAN AERONAUTICAL LABORATORIES ZAHM 2T, 



aeroplane by a pilot in practical flight. This instrument may help 

 to determine the most suitable mechanism for a standard control. 



The shop and the engine testing houses contain nothing that need 

 be reported. The engine torque and thrust were measured by 

 ordinary mechanical methods, and no special apparatus was used 

 to furnish a stream of cooling air, as in the British laboratory. 



Other German aeroitautieal laboratories worth passing mention 

 are : the testing department of the Zeppelin Airship Co. ; the aero- 

 dynamical laboratory used by Prof. Reissner of the technical high 

 school at Achen ; the laboratory in charge of Major v. Parseval in 

 the high school at Berlin ; the experimental plant of Prof. Dr. Fr. 

 Ahlborn, at Hamburg. The Zeppelin laboratory is not. under any 

 consideration, open to visitors from abroad ; and as to the others 

 just mentioned, I had time only for a brief visit to Ahlborn's place. 

 Ahlborn's experiments have been confined mainly to determinations 

 of flow about models in a tank of water. The results are well por- 

 trayed in numerous excellent photographs and publications, the 

 best of which are in the Smithsonian Institution. His apparatus and 

 photographs and those at the National Physical Laboratory in 

 England are, for hydromechanical studies, the most instructive that 

 have yet come to my notice, except perhaps the more restricted ones 

 of Hele-Shaw. For stream-line delineation in air, however, the 

 classical apparatus and methods of Marey have not yet been sur- 

 passed, though more precise instruments of this nature are much 

 to be desired. 



CONCLUSION 



In closing I would gratefully acknowledge the courteous assistance 

 extended to Lieut. Hunsaker and myself, by the American Embassies 

 at London, Paris and Berlin, by the aero clubs in those cities, and by 

 the directors of the laboratories and factories we visited. We are 

 especially indebted to Mr. G. F. Campbell Wood, foreign representa- 

 tive of the Aero Club of America, at Paris, and to Major G. J. F. 

 Von Tschudi, of the German y\rmy, Director of the Plug und Sport- 

 platz at Johannisthal, for many kind services which enlarged our 

 opportunities and facilitated our work in France and Germany. 



