98 LF. H. Bigelow—The Earth a Magnetic Shell. 
Each of these hypotheses is regarded as improbable and 
unproven. Also Hall proposes that the exponent of the dis- 
tance in the law of gravitation is not precisely 2, but about 
2,000,000, 1574, as the compensation for at least two or three 
discrepancies. 
To these secular motions may be added the short period 
variations of the terrestrial latitudes, as given by Chandler in 
the periods of 365 days, 428 days, and 12 years. All attempts to 
assign to these a suitable physical cause, whether meteorolog- 
ical or geophysical, have failed to meet with acceptable results. 
Now the outcome of my research into the magnetic varia- 
tions is to show that two systems of mechanical forces exist in 
the ether at the surface of the earth, besides gravitation, and 
that these must be added to account for all the known forces at 
work. The medium that sustains the gravity stress also contains 
stresses due to the two types of radiant energy as impressed by 
the solar action upon the ether. The discovery of the exact 
form of the gravitation stress and the radiant magnetic stress 
is yet to be made, on the supposition that the Hertzian electro- 
magnetic stress is now understood. The order of the mechan- 
ical forces at the surface of the earth is as follows: 
The earth’s gravity, g = 980°60 cm. = 386 inches per sec. 
The sun’s acceleration, # = 0°5929 cm. = 0°2334 inch per sec. 
The electro-magnetic field near the poles Hp = 0°00070 cm. 
= 000028 10. 
The electro-magnetic field in middle latitudes ZHm = 
000030 cm. = 0°00012 in. 
The polar magnetic field = 0:00035 cm. = 0°00014 in. 
Saheb k aT eee sengeibs' ee 
Ratios, f = aaa AHp = 347" Arn = 1976" AN EL == Thy 
To explain the periods, we have, 
365 days, the couples of the electro-magnetic field move up 
and down the earth with the sun’s annual declination ; 
428 days, the elasticity of the shell of the earth under gravi- 
tation is believed to give this mertia period ; 
12 years, the variation of the polar magnetic field in the sun 
spot cycle is proven. | 
See this Journal, Dec. 1894, p. 448, and a large literature 
on sun spots, auroras, magnetic forces. This field varies at 
least 75%, and is attached to the midlatitude regions of the 
earth, appropriately to displace the axis of rotation. _Chandler’s 
dates of maximum are so closely associated with the dates of 
the maximum of sun spots for the last half century as to claim 
careful consideration. 
