6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93 



connected by means of a pipe. A number of small holes were made in 

 both surfaces, of which one at a time was opened. Two such testing 

 planes were used ; both were i^ inches wide, one 4^ inches long, reach- 

 ing entirely across the tunnel, the other 2^ inches long. The testing 



Section x-y 



^ 



Fig. 4. — Pressure measuring apparatus used by Irminger and Vogt. 



planes were placed in the middle of the tunnel and could be set at 

 different angles that were indicated by a pointer on the outside. 



Measurements of pressure distribution were also made on bodies of 

 various shapes, as prisms, spheres, etc., and on models of buildings 

 and gas tanks.'' 



' Ingenioren, p. loi, Copenliagen, 1894. 



Inst. Civil Eng., Minutes of Proc, vol. 118, pp. 468-472, 1894. 

 Engineering, vol. 60, pp. 787-788, illus., London, Dec. 27, 1895. 



