256 
temperature period, by acting upon this view, may be regarded 
as affording strong evidence in its favour. 
With regard to the probable cause of the variability of the 
short period, the author remarks that the subject is one of 
great difficulty, for, while the facts seem clearly to belong to 
the domain of astronomical science, he has found it impossible 
to frame any hypothesis to account for them without calling 
in the aid of some principle which has not hitherto been 
applied to the explanation of astronomical phenomena. It 
is therefore not without considerable hesitation that he 
ventures to observe that the facts would perhaps be best 
explained by supposing — 
1st. That a ring of nebulous matter exists differing in 
density or constitution in different parts, or several, masses 
of such matter forming a discontinuous ring, circulating 
round the sun in a plane nearly coincident with the plane 
of the ecliptic, and at a mean distance from the sun of about 
one-sixth of the radius of the earth’s orbit. 
2nd. That the attractive force of the sun on the matter of 
this ring is alternately increased and diminished by the 
operation of the forces which produce the solar spots, being 
greatest at the times of minimum solar spot frequency, and 
least when the spots are most numerous. 
3rd. The attractive force being variable, the dimensions of 
the ring and its period of revolution round the sun will also 
vary, their maximum and minimum values occurring respect- 
ively at the times of maximum and minimum solar spot 
frequency. 
In reference to the nature of the varying attractive force, it 
is not improbable that the matter of the supposed ring may be 
highly diamagnetic, and being much nearer to the sun than 
any of the known planets, of much greater bulk and lightness, 
and being subjected to a much higher temperature, it will be 
very sensibly affected by the changes which take place in the 
magnetic condition of the sun, and when interposed between 
