PAPER BY PROF. HAGEN. 



21 



these, however, as above mentioned, the measures were executed twice. 

 The resulting values of z and r are given in the last columns. The 

 other letters correspond to those above given : 



In order from this to find the pressure on thu unit of surface, or 1;, we 

 have to assume the lever arm «=0.8i705 inch, as already shown above. 

 The following table contains the values of R, as well as the reduced r, 

 and the surfaces of the disks F, as to which latter it is to be noticed 

 that after more careful measuremeuts the radii of the second and third 

 disks resulted 1.745 and 2.245: 



Table I. 



r i. e., Reduced to standard density of air. 



In order to avoid too small numbers these values of Jc are given too 

 large, and must be divided by one million in order to present the desired 

 constant factors, which, multiplied by the squares of the velocities in 

 inches, will give the pressures in loths for each square inch of the disk. 

 This same multiplication of A: is also continued in the following para- 

 graphs. 



Many days later I repeated these observations with the same disks. 



The results were — 



