OF FLUIDS ON THE MOTION OF PENDULUMS. 



[85] 



Dubuafs experiments on spheres oscillating in water. 



70. If we strike out the experiments with the large sphere, which cannot well be compared 

 with theory for a reason which will be explained further on, it will be observed that in seven out 

 of the eight groups of experiments left, the signs in the last column are regularly minus. 

 The preponderance of negative errors could be destroyed by using a much smaller value of 

 y/ix in the reduction. We have seen, however, that the value of y/V deduced from Cou- 

 lomb's experiments on the decrement of the arc of oscillation of disks satisfied almost exactly 

 Bessel's observations of the time of oscillation of a sphere about two inches in diameter 

 oscillating in water. The very small errors which remained in this case had both the sign +, 

 whereas in Dubuat's experiments on the 1-inch and 2^ inch spheres, the errors, which are far 

 larger, have all the sign -. Since the experiments of Dubuat and Bessel, though made under 

 similar circumstances, do not lead to the same result, it is of course impossible for any theory to 



