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matter is principally of a magnetic, and but slightly of a 
thermal character. 
It is suggested that the greater range of variation of the 
magnetic as compared with the temperature period may be 
due to the inertia and elasticity of the great currents of air, 
the inertia tending to lengthen the temperature period and 
the elasticity to shorten it ; but as the inertia will act with 
greatest effect when the magnetic period is at its minimum, 
while on the other hand the elasticity will be most effective 
when this period is at its maximum, the result will be a range 
of variation of the temperature period, somewhat less than 
that of the magnetic. 
Adoping for the present the maximum and minimum 
values of the temperature period as being determined with 
greater accuracy than those of the magnetic period, the 
greatest and least values of the sidereal period of revolu- 
tion of the ring will be 29' 12 and 22‘08 days respectively. 
From these numbers we find that the greatest distance of the 
ring from the sun is 0.185, the radius of the earth’s orbit 
being taken as unity; the least distance 0.154; and the 
mean O' 169. Taking Mr. Hind’s value of the mean distance 
of the earth from the sun, namely, 91,328,600 miles, we have 
Greatest distance of the ring = 16,921,000 miles. 
Least „ ,, = 14,068,000 „ 
Mean ,, ,, = 15,494,500 „ 
and the range of movement to and fro in a radial direction 
= 2,853,000 miles. The greatest attractive force of the sun 
on the ring being taken as unity, the least will be 0 691. 
The difference is therefore nearly one-third of the maximum 
amount. It will be evident that this difference may be 
regarded as a measure of the forces which are concerned in 
the production of the solar spots. 
The results of the elaborate investigations of the motions 
of the planet Mercury, made by INI. Levemer, led that ac- 
complished mathematician to attribute a certain unexplained 
