W. A. Norton on Molecular Physics. . 69 
the point of the earth’s photosphere directly underneath the 
sun.“ The other set of currents, have a maximum of effective 
action at the autumnal equinox, and, considered individually, a 
minimum at the vernal equinox.’ For at the autumnal equinox 
the most advanced point of the earth’s surface, upon which the 
impulses of the ether fall normally, will lie 234° to the north of 
he equator; and at the vernal equinox it will lie 234° to the 
south of it. Owing to the annual change in the intensity of the 
radial currents, the diurnal variations, both of the horizontal 
force and declination of the needle, that occur during the fore- 
noon and afternoon, are greater in the summer than in the win- 
A. (See Prof. Bache’s Discussion of the Magnetic Obser- 
vations made at Philadelphia, in 1840 to 1845, p. 45.) Past 
€ would here call attention to a special fact, from which it 
results that the currents developed by the ether, both on the 
side of the earth toward the sun, and on the opposite side, are 
especially effective about the equinoxes. Itis that, for a consid- 
erable period before and after these epochs, such currents, excited 
at any one place, have very nearly the same direction, and so 
Cooperate more effectually. (See additional remark on page 72). 
Among the annual variations of declination may be specified an 
fasterly movement of the needle at the hour of 6 A. M. from the 
annual variation that has been detected is an augmentation of 
the mean monthly intensity of the horizontal force, from winter 
_* The Precise epoch when the radial currents are most effective should vary 
shone, atitude Pt the station. It is plain that near the tropic of Cancer it 
some we 
P , 
‘shoul weeks before or after the summer solstice; for at summer. 
Solstice at the hour of noon, the currents, or wav: each the station from the 
Pag t points of the apie ety that receive the agg rays, should exactly neu- 
other. The epoch, or epochs, in question, it is obvious shoul 
~ as we recede from the Torrid - observations made at 
tal indicate that the radial currents are most 
ee ii on rizon n di a“ 
effective in determining the diurnal variation of the horizontal force about a month 
ore ; i 
i t with 
. 1 ust a8 with the radial currents, the epoch tumnal 
the latitude, and in the lower latitudes should occur before and after the au — 
. : ap . 
