10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93 



The air speed was measured with a pitot-static tube, connected with 

 an extremely sensitive manometer." This consisted of two thin metal 

 cups, inverted over coal-oil and supported from opposite ends of a 

 weighing beam. Two tubes, one from underneath each cup, were 

 joined respectively to the inner and outer tubes of the speed nozzle. 

 To test the accuracy of this instrument a " balloon anemometer " was 

 devised. A toy balloon floating downstream intersected on its way 

 two thin pencils of light focussed on the moving plate of a long 

 camera constructed for that purpose. This was an adaptation of the 

 ingenious chronograph previously invented by Dr. Zahm for his re- 

 searches on the speed of bullets.'" 



The manometer was also used for the study of pressure distribution. 



Several aerodynamic balances were developed, among them the wire 

 suspension balance, now in general use, and the bell crank balance, 

 now often called the N. P. L. balance. It was called the " universal 

 pressure balance " in 1902, and consisted of a bell crank with hori- 

 zontal axle mounted on knife edges above the tunnel, having a gradu- 

 ated horizontal arm with scalepan and sliding weights, and a vertical 

 arm running down through a streamline wind shield to hold the models 

 in the air stream. 



The laboratory was built and equipped early in 1901 and a descrip- 

 tion was communicated to the American Association for the Advance- 

 ment of Science June 30, 1932, and was privately printed (200 copies) 

 in a small pamphlet which is now a great rarity." 



MattuUath died in December 1902, and the flying-boat project was 

 abandoned, but the scientific work in the laboratory went on inter- 

 mittently until 1908. Money grants for special researches were made 

 by the Smithsonian Institution and the Carnegie Institution in 1904 

 and 1905. Results of the investigations were communicated to scientific 

 journals and societies. The most important of these was Dr. Zahm's 



'■ Exhibited before the Washington Philosophical Society, May 24, 1902 ; 

 described in Phys. Rev., vol. 17, pp. 410-423, December 1903. In this paper, 

 p. 417, the term " wind tunnel " is used for the first time. 



" The resistance of the air determined at speeds below one thousand feet a 

 second, with description of two new methods of measuring projectile velocities 

 inside and outside the gun. Thesis, Johns Hopkins Univ., 46 pp., illus., 1898. 



" New methods of experimentation in aerodynamics ; outline of some experi- 

 ments made by H. MattuUath and A. F. Zahm, at the Catholic University of 

 America. Paper communicated to the meeting of the American Association for 

 the Advancement of Science, at Pittsburgh, June 30, 1902. 12 pp., illus., signed 

 A. F. Zahm, Washington, D. C, 1902. 



