COR 
XI. 
ON A POSSIBLE CONNEXION BETWEEN THE ERUPTION 
OF VESUVIUS AND THE EARTHQUAKE AT SAN 
FRANCISCO IN APRIL, 1906. 
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[COMMUNICATED BY PROFESSOR A. W. CONWAY, M.A. | 
[Read, May 15; Received for Publication, May 18; Published, June 15, 1906.] 
Tue following is a brief account of some simple experiments with 
rotating bodies, and an application of the principles illustrated by 
them to explain a possible connexion between seismic disturbances 
at different localities. 
A perfectly balanced teetotum or top will spin about the axis 
of its spindle with great regularity. If a weight be attached to 
one side, it will spin with a “wobble.” By placing an equal 
weight exactly opposite the first, regular spinning may be restored. 
The same result may be obtained by placing several equal weights 
at equal distances round the circumference.! 
A hollow teetotum was made 2 inch deep, and 11 inch in 
diameter. This was made with great care, and could be covered 
by a plate which screwed on. A number of steel “ ball-bearing ” 
balls were also obtained. 
1. The teetotum was set spinning, and spun with perfect 
evenness. While it was spinning, a ball of 1 inch diameter was 
dropped in. At once the teetotum began to wobble, and the 
ball could be heard running round the inner edge. A second ball 
of the same size was then dropped in; a slight movement of the 
balls was heard which ceased at once, the wobble disappeared, and 
once more the teetotum spun perfectly evenly, just as before 
it had been disturbed. The balls were found to have placed 
themselves at the opposite ends of a common diameter. The same 
1 Natwre, April 19th, 1903. 
SCIENT. PROC. R.D.S., VOL. XI., NO. XI. iB 
