Nipher — Method of Measuring Pressure on a Structure. 9 



The work of setting the pressure board, reading the posi- 

 tion of the wind vane, the index of the spring balance and 

 the angle of pull, was done by Professor A. H. Timmerman, 

 formerly ray assistant, and now Professor of Physics in the 

 Rolla School of Mines. It was necessary to give constant 

 attention to all of the indications to be read, in order that 

 values practically simultaneous could be obtained when an 

 adjustment was secured. 



The pressure board was divided into 108 four-inch squares. 

 The vertical rows of squares were numbered from 1 to 

 12, the former being nearest to the axis of rotation. The 

 horizontal rows of squares 

 were lettered from a to i, the 

 former being at the top. At 

 the center of each square a 

 hole f of an inch in diameter 

 was bored through, and two 

 disk collectors could be me- 

 chanically coupled to each 

 other through any one of them 

 so as to close it in an air-tight 

 joint. All other holes were 

 closed by closely fitting corks, 

 flush with the front side of the 

 board. One collector was fur- 

 nished with a screw, which 

 was seated in a screw hole in 

 a hub attached to the other 

 collector, and fitting into the 

 hole in the pressure board. 



The manner of mounting these collectors is shown in Fig. 2, 

 where the fragment of wood between represents the pressure 

 board. Rubber tubes passed down through the iron pipe into 

 the car and connected the disks on the front and rear of the 

 pressure board with separate pressure gauges. In this way 

 the pressure could be determined at 109 different points on 

 the board, the pressure in front being measured separately 

 from that on the back of the board. 



The pressure gauges were four in number. The cisterns were 



Fig. 2. 



