OF WHICH VARIOUS SUBSTANCES ARE SUSCEPTIBLE. 
79 
different substances similar to the above, and found their influence on the 
vibrations very decided, although the differences in their respective magnetic 
energies was not very apparent. The substances tried, with the respective 
number of vibrations, and their comparative energies as deduced from the for- 
mula, are given in the ensuing Table. 
Table III. 
Substances. 
Vibrations from 45° 
to 10°. 
Comparative energies 
as deduced from 
formula. 
Distilled water, temp. 1 
20° Fahr / 
330 
0.27 
Honduras mahogany .... 
308 
0.36 
Statuary marble 
306 
0.37 
Freestone 
308 
0.36 
Annealed glass, -rV-inch 1 
thick j 
310 
0.35 
18. By employing the above substances in larger masses, the effect on the 
bar seemed to be greatly increased : although the difference in the compa- 
rative energies of wood and marble, the only two substances which I had an 
opportunity of trying, is still not very great. In the following Table are given 
the results of some experiments with a ring of statuary marble of 1.75 inch 
thick, and with a similar ring of Honduras mahogany, as compared with the 
influence of two rings of the same substances of only one fifth of an inch in 
thickness. 
Table IV. 
Substances. 
Wood. 
Marble. 
Thickness of ring in inches .... 
0.2 
1.75 
0.2 
1.75 
Vibrations from 45° to 10° .... 
308 
280 
306 
265 
Ratio of magnetic influence as 1 
deduced from formula . . . . / 
0.36 
0.50 
0.35 
0.59 
19. The influence of the substances being observed to depend in great 
