Prof. Norton on Molecular Physics. 273 



impulses of the sether fall normally will lie 23J° to the north of 

 the equator, and at the vernal equinox it will lie 23^° 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 winter. 

 The maximum variations occur after the summer solstice, and 

 the minimum after the winter solstice. By reason of the an- 

 nual change in the effective action of the other set of currents, 

 the morning variations of the horizontal force and declination 

 (i. e. for a certain interval before and after 6 a.m.) are greater at 

 the autumnal than at the vernal equinox. The more effective 

 action of these currents at the autumnal than at the vernal equi- 

 nox is conspicuously seen in the higher maximum of the hori- 

 zontal force at 5 a.m. to 6 a.m., and the lower minimum about 

 10 a.m. (See Prof. Bach's ' Discussion of the Magnetic Obser- 

 vations made at Philadelphia in 1840 to 1845/ p. 45.) 



We should here call attention to a special fact from which it 

 results that the currents developed by the sether, both on the 

 side of the earth towards the sun and on the opposite side, are 

 especially effective about the equinoxes. It is that for a consi- 

 derable period before and after these epochs, such currents, ex- 

 cited at any one place, have very nearly the same direction, and 

 so cooperate more effectually. (See additional remark on p. 276.) 



Among the annual variations of declination may be specified 

 an easterly movement of the needle at the hour of 6 a.m. from 

 the winter to the summer solstice. The author has already shown, 

 iu his previous paper (Silliman's Journal, vol. ix. p. 196), that 

 such an effect should result from the action of the radial currents. 

 Another annual variation that has been detected is an augmen- 

 tation of the mean monthly intensity of the horizontal force, from 

 winter to summer. (Professor Bache's Discussion, &c, p. 59.) 

 To understand how this may result, it is to be observed that 

 since the effective radial currents steadily increase in intensity 

 from winter to summer, and since the action in the afternoon of 

 each day is to augment the horizontal force, and in the forenoon 

 to diminish it, whatever effective residual current may remain 

 as the result of the entire action of the currents in question 

 during a single day, must have the direction of the currents 

 that augment the force. By the continual accumulation of 

 such residual currents, there must accordingly be a tendency to 

 an increase in the intensity of the horizontal force from winter 

 to summer. 



But the other system of radial currents should also cooperate 

 with these in producing variations in the intensity of the hori- 

 zontal force from one month to another. Since the effective 



