12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 62 



Other English aeronautical laboratories worth mentioning are 

 those of the Northampton Polytechnic Institute, London, and of the 

 East London College. For want of time I did not investigate these ; 

 but as their resources are very moderate and their reports have been 

 irregular and meager, it is doubtful whether they contain any equip- 

 ment materially worth adding to what has been hitherto described. 



FRENCH AERONAUTICAL LABORATORIES 

 The Laboratoire Aerodynamiqne Eiifel consists of a single build- 

 ing with offices, a wind tunnel and various appurtenances, there being 

 no workshops in the establishment. The wind-tunnel room measures, 

 in round numbers, 4c by 100 feet, by 30 feet high ; the three office 

 rooms and garden cover about half as much additional space. Two 

 wind-tunnels, a large and a small one, placed side by side, occupy 

 the center of the room. They are placed well above the floor, to 

 admit of a more nearly symmetrical flow of air. Considerable fur- 

 niture — shelves, drawers, etc. — is placed about the walls ; but the 

 body of the room is kept somewhat free of obstructions to secure 

 a less disturbed circulation. 



Each tunnel comprises three main parts : the short bell-mouth 

 intake, the model chamber, the long bell-mouth exit. The air from 

 the room traverses the intake through honey-combs placed at eitljer 

 end of the bell-like form ; then passes at its maximum speed in 

 uniform rectilinear current across the model chamber ; then flows in 

 gently expanding stream and with diminishing speed onward to the 

 larger end of the exit, where it encounters the fan which drives it 

 with replenished energy into the open room. The model chamber is 

 thus seen to be an enlargement of the tunnel proper, spacious enough 

 to accommodate observers, and so sealed from the surrounding room 

 as to have the same barometric pressure as the inflowing current at 

 its narrowest section. 



This type of tunnel, adopted by Eift'el after mature experience, 

 has been patented by him as having features of considerable value. 

 He prizes particularly the vacuum chamber for the observers, and 

 for the freer flow of air about the models, uninfluenced by constrain- 

 ing walls. He also prizes the expanding exit, or " dift'usor," for 

 slowing the air as it approaches the fan and exhausts into the room, 

 thus realizing great economy of power in maintaining the circula- 

 tion. It is doubtful, however, whether any of the main features of 

 Eiffel's tunnel are patentable in America. The bell-mouth entrance 

 and exit have been known here many years. The vacuum chamber 



