220 Trans, Acad. Set. of St. Louis. 



was transmitted from the collector to the air chamber above the 

 water in the cistern, and an increase of pressure was shown 

 by the rise in the level of the water in the inclined tube. 

 The whole apparatus was carried on a carpenter's clamp of 

 wood, which could be clamped to the window sill of the car. 

 The cistern and inclined tube were pivotally mounted on a 

 standard attached to the clamp, and furnished with a level 

 and with a duplicate tube and cistern which served also 

 as a level. By this means the frame carrying the cisterns 

 and tubes could be kept in level while readings of pressure 

 were being made. The collector was mounted on a light 

 wooden channel-bar, sliding in guides attached to the clamp. 

 The rubber tube was laid in the channel of this bar. 'J he 

 bar could be thrust out to various distances, so that the col- 

 lector could be set to a known distance from the side of the 

 car. This distance could be varied from to 30 inches. At 

 the former distance the axis of the collector was at the gen- 

 eral surface of the car. The wooden channel-bar was occa- 

 sionally broken by collision with bridges, and a supply of 

 such bars was always carried. 



The measurements were made on passenger trains and on 

 freight trains on various roads. Many trips were made from 

 St. Louis to Burlington, on the St. L., K. and N. VV. R. R. 

 and from St. Louis to Chicago and Cairo on the Illinois 

 Cential. Some work was also done on the St. Louis and San 

 Francisco and on the Wabash railroads, where advantage was 

 taken of journeys on other business. Ihe officials of all 

 these roads afforded every assistance in the prosecution of 

 this work. The Illinois Central R. R. finally fitted up a 

 special car which was delivered to us at East St. Louis, and 

 it was placed in any part of any train we might select upon 

 this road. 



The greater part of one summer was devoted to the study 

 of various wind pressure problems by means of this car, 

 which was in motion during most of the daylight hours of 

 every day.* 



During most of this work, the open end of the pressure 



♦ Trans. Acad. Sci. of St. Louis, No. 1, Vol. VIII. 



