PAPER BY PROF. HAGEN. 



From this table there results as the most probable values 



a = 2.2639 

 /i = 0.009410 



The values of 1c computed from this are giveu in the column A; from 

 the differences in the next column, with reference to the observed values 

 of k, there results the probable error 0.0252, and we find the probable 

 error of a equal to 0.01338, or about i per cent., and of ft equal to 

 0.000719, or about lh per cent. 



Although the reliability of these results, especially in their applica- 

 tion to still larger surfaces and greater velocities, leaves much to be 

 desired, still scarcely any important higher degree of accuracy is to be 

 attained with apparatus that is similar to that above described. On 

 the other hand the concluded law of resistance would be in an impor- 

 tant degree confirmed or corrected, if on a firm rod in front of a loco- 

 motive, disks are fastened, whose pressure could be measured by the 

 tension of a spring, while the milestones on the roadside would serve 

 very conveniently for the determination of the velocity.* 



* [This experiment has been carried on recently by Wild and others, but the 

 resulting value of k is not so reliable as that deduced from observations with large 

 whirling machines.— C. A.] 



