1864. | Henrscuen on the Solar Spots. 233 
mentioned acceleration in the (no doubt exceedingly rare) matter of the 
solar atmosphere at the level of the photosphere, as the measure of the 
final result of its impact and friction, And on the theory of the frictional 
generation of the sun’s heat, it is the amount of vis viva so delivered 
into the sun to which we have to look for the maintenance of its supply 
of heat. It would be superfluous to adduce arguments, to show the 
utter inadequacy of the cause to produce the effect. If this be all, the 
origin of the solar heat is as much a mystery as ever. 
III. The intermediate hypothesis may be very summarily dismissed. 
It has not the merits of either extreme, and is in contradiction to 
both. It supposes a permanent west wind on the equator, and is there- 
fore inconsistent with any Htesian theory (of a system of trades and 
anti-trades)—and a permanent set of the whole atmosphere, beyond a 
given latitude, to the westward, equally contradictory to the theory of 
an external drift, the result of planetary circulation. 
Between the two extreme hypotheses there would seem to exist a 
crucial means of discrimination. The first undoubtedly seems to 
presume an average tendency of the spots towards the sun’s equator, 
while the latter involves no conclusion either to that or the contrary 
effect. On this point however, observation is not very positive. Pro- 
fessor Peters is of opinion that there 7s such a tendency, while Mr. 
Carrington seems to think the contrary. His synoptic table (Observation 
of Solar Spots, p. 220) exhibits an average, though very small prepon- 
derance, in favour of a general movement towards the poles, on either side 
of the equator—but the individual differences, to whatever cause 
attributable are so very much greater, as to destroy all confidence in 
sucha conclusion. From the result of Professor Fearnley’s observations 
on the spot of 1857, whose periods of return went on successively 
increasing on each reappearance of the spot, it may fairly be concluded 
that the spot was receding from the equator. Unfortunately I have not 
been able to ascertain whether such was really the case. 
Mr. Carrington puts forth a surmise (p. 248) whether some part of 
the irregularity in the maculiferous activity of the sun may not arise 
from the action of Jupiter on the zodiacal light. To appretiate the 
probability of this we have only to consider—1st. That the zodiacal 
light can hardly extend beyond the orbit of the earth—assuredly not 
its denser portions. 2nd. That its medial plane is that of the sun’s 
equator, which is inclined 5° or 6° to the orbit of Jupiter, so that it is 
only when near their common node that any action, even on the 
infinitely attenuated portion of it which may reach so far, can take 
place. And 3rd. That whatever be the form of the zodiacal light in 
section, we have no reason to believe it other than circular in plan. 
Let us suppose, however (and such a supposition has not been 
deemed inadmissible in attempting to account for the periodical return 
of meteors), the existence of an elliptic ring of vaporous, nebulous, or 
small planetary matter, with such a major semiaxis (4°979) as cor- 
responds to a periodic time of each of its particles == 11-11 years; of 
such eccentricity as to bring its perihelion within the limits of the 
solar envelopes; and revolving either in the plane of the ecliptic or 
in some other plane at a more considerable inclination to the sun’s 
