24 



THE MECHANICS OF THE EARTH'S ATMOSPHERE. 



Directly following the above, the same observations were repeated 

 with the square disk of 5 inches on a side with the following results: 



Jb'roui luese latter there finally resulted 



A-= +2.4491. 



The results thus far obtained warrant the suspicion that for equal 

 areas of the disks, the resistance becomes smaller the shorter is the de- 

 viated path that the air must describe in order to pass around the 

 disk. Hence it is to be expected that the resistance would become 

 especially small for long and narrow disks. Consequently I took a 

 pair of disks 1 inch broad and 10 inches high, which therefore had the 

 same area as the square disks of 4 inches on a side. These I allowed 

 to run interchangeably with the square disks and under equal loads, 

 but most unexpectedly the velocity of the square disks was always 

 somewhat greater than the narrow ones. This was so much the more 

 remarkable as the square ones, on account of the greater distances 

 from the axis of rotation, were expected to show a greater resistance. 



As at first I allowed these long disks to run under only two different 

 loadings, I found 



For the feeble load the velocity had shown very discrepant values. 

 Therefore the repetition of the observation was important, and for 

 greater security this was done on the following day for six different 

 loads. 



