_ of the needle is wester 
Diyos ec 
P. E. Chase on Mechanical Polarity. 315 
thermal meridians and meet at the thermal pole, I constructed 
a compound disc (m), of two circular segments, inclined to each 
other at an angle of about 80°, with which I tried the following 
experiments :— 
B. Spherical-angular disc. 
a. Axis in magnetic meridian. 
14, If the disc is so placed, with its opening towards the 
south, ihat its angle is bisected by the meridian, the current- 
polarity carries the needle in the same direction as the motion of 
the top of the ring. 
15. If the opening of the disc is turned to the north, the ap- 
paratus remaining in other respects as in the last experiment, the 
current-polarity is reversed (as in EB 
xp. 8). 
16. Placing the disc equatorially, [am unable to discover any 
current-polarity. 
7. Inclining the dise towards N.W. and S.E., the needle 
moves towards the east, whether the opening of the disc is to- 
wards the north or towards the south. 
18. If the inclination is towards N.E. and S.W., the motion 
pa 
Experiments 14 to 18 are perhaps the most interesting and 
important of the entire series. Exp. 14 represents the direction 
the gravitation currents that tend to restore the equilibrium 
which is continually disturbed by the thermal radiation of 
the northern hemisphere, while Exp. 15 represents the like di- 
