86 P. E. Chase on influence of Gravity on Magnetic Declination. 
Ww 
fect than that now used. The second characteristic of the ine- 
quality consists in the earlier occurrence of the maxima and 
minima in winter than in summer. @ winter curve precedes 
the summer curve by about one and three-quarter hours.” [Ibid., - 
13.] 
Regarding, therefore, the air and wether over any given mag- 
netic meridian, during the day hours the intertropical and dur- 
ing the night the extra-tropical portions will be most drawn 
toward the sun, and the following deflections will be thus pro- 
duced in the portions nearest the equator : 
6tol2am. I12to6rpm Gtol2p.m. I2to6a.u 
Northern zones, S.E. .W. .H. S.W. 
Southern * N.E. N.W. N.E. N.W. 
The night-disturbances, whether from variations of temperature 
or from simple fall toward the sun (the distance fallen varying 
as the square of the time from midnight), will be very slight. 
"he earth’s rotation, centrifugal force, and the atmospheric iner- 
ia, tend to throw each of the phases forward and to increase 
he magnitude of the westerly, while they diminish the easterly 
eflections. If these modifications were sufficient to override the 
light easterly tendency at 6 to 12 P. M., and to advance the 
phases one hour, the disturbances would assume the following 
forms, the change between 7 p. M. and 1 A. uw, being scarcely, if 
at all, perceptible: : 
wm Och ct pd 
SoS 
