Oct. 28, 1886] 
inquiring into. Each has its own significance, and might 
be made the subject of a separate, and not unfruitful, 
study. 
Prominences and spots are, by our author, connected 
together as cause and effect, but in the inverse order of 
their probable occurrence. There are strong grounds for 
the belief that the initial disturbance is that which occa- 
sions a spot, eruptive appearances ensuing consequentially. 
But, if M. Schulz’s account of the matter were correct, no 
spot could arise without an introductory display of spon- 
taneous and preliminary flames. Prominences, in his 
scheme, are composed exclusively of the green coronal 
gas “1474.” It is true that in the spectroscope lines of 
hydrogen and helium are visible, but their meaning, we 
are told, has been misinterpreted. They take their origin, 
not from the body of the prominence, but from the glowing 
sheath with which the resistance of the solar atmosphere 
to its upspringing encompasses it. This surprising con- 
tention refutes itself. The implied resistance would, in a 
few seconds, shatter into inconspicuousness the rushing 
volumes evoking it. ‘‘ Quiescent prominences,” more- 
over, would on this theory be impossible; yet they are 
often plainly visible, for weeks together, in virtually un- 
changing forms ; to say nothing of spectroscopic incom- 
patibilities, too obvious to need dwelling upon. 
The mechanical power consumed in the projection up- 
wards of these bodies is derived from the expansive force 
of gas escaping from tremendous pressure. In dilating, 
however, it loses heat, and at such a rate that by the time 
the pressure upon it is reduced from ten million terrestrial 
atmospheres to one tenth of an atmosphere, its tempera- 
ture has fallen from 12,000° to — 216° Centigrade. The 
ensuing condensation to the liquid and thence to the 
solid state brings about a fall of “1474 snow” upon the 
photosphere. When the shower is a light one, a “ pore” 
is the consequence ; when it is heavy and long-continued, 
the cold falling matter reaches the liquid sheet beneath, 
a group of “slag-islands” is formed from the chilly con- 
tact, and a spot becomes apparent to distant onlookers. 
The overlying photospheric clouds then arrange them- 
selves, under the influence of atmospheric currents, into 
the characteristic funnel-shape of the penumbra, at the 
bottom of which lies the obscure solid nucleus, more or 
less veiled in dense absorbing vapours. 
Improbability raised to an infinite degree becomes im- 
possibility ; and we may safely assert that that degree 
has here been reached. Criticism is silent in the presence 
of a supposition so fantastic as that of a substance pre- 
sumably far less condensable than hydrogen existing 
frozen in the very depths of the thrice-heated furnace of 
the sun. 
So much for prominences and spots : we now come to 
facule. They are regarded by M. Schulz as mere optical 
effects of irregular refraction in the agitated vicinity of 
spots. Yet the plainest ocular proof of their being real 
elevations above the general level of the photosphere is 
afforded by their not unfrequent visibility as projections 
from the smooth border of the limb, as well as by Dr. 
De la Rue’s relief-pictures obtained by the stereoscopic 
combination of photographs. 
The (not undisputed) higher equatorial temperature of 
the sun supplies M. Schulz, as it supplied Zollner, with a 
“ trade-wind ” circulation, by means of which the retarded 
transport of spots remote from the equator are, with some 
difficulty, accounted for. Their slight displacements in 
latitude prescribe the mode of the sun’s bodily circulation. 
A stupendous system of vorticose currents—set going by 
differences of specific gravity through surface-cooling—is 
disposed so as to impel such objects slowly towards the 
poles from about 15° of north and south latitude, while 
minor equatorial whirlpools give the observed opposite 
drift within those limits. But such an arrangement, even 
were it otherwise possible, would reverse Carrington’s 
noted law of solar rotation, the angular rate of which 
NATURE 
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would, under the supposed circumstances, guécken with 
advance poleward, while the maximum retardation would 
occur somewhere between ten and twenty degrees of 
latitude. 
This rolling movement from within outward of the 
entire substance of the liquid solar globe, save a small 
dense nucleus, serves, however, a further purpose. It 
explains the spot-period. 
The occurrence of spots, it must be remembered, de- 
pénds primarily upon the escape of “1474” gas (which 
we may designate “coronium”) from the interior. But 
how does it get there? M, Schulz’s reply is to the follow- 
ing effect. 
Coronium has a powerful affinity for a certain hypo- 
thetical solar constituent described as “ spot-stuff.” In 
middle and high latitudes a temperature as low perhaps 
as g000° C. permits combination which accordingly takes 
place freely over a vast area. Huge masses of a com- 
pound of coronium with “spot-stuff” thus enter into the 
general circulation, and are gradually carried down to 
depths where a temperature enforcing dissociation is en- 
countered, giving rise to the formation, under enormous. 
pressure, of gigantic bubbles of pure coronal gas. By 
their variously-conditioned outbursts these finally occasion 
prominences and spots, which are more or less numerous 
according as the distribution of ‘“‘spot-stuff” is more or 
less plentiful. Admitting some degree of permanence in 
its localisation, and assuming that the great vortices. 
whirl once completely round in eleven years, the spot- 
cycle is established. The equatorial spot-and-prominence 
minimum finds its va¢zona/e in the higher temperature 
by which the occurrence of chemical association in any 
part of the separate equatorial vortices is prohibited. 
We have endeavoured, while omitting details which it 
would be waste of time to dwell upon, to do no injustice 
to M. Schulz’s ideas in our brief sketch of them. Yet it 
is difficult to treat them quite seriously ; and we confess 
to a feeling of regret in seeing a writer of M. Schulz’s 
ability and acquirements apply them to the elaboration of 
so baseless a series of hypotheses—baseless in this sense, 
that they rest upon a number of postulates which few 
will be disposed to allow. With sufficient liberality of 
assumption almost anything can be explained on any 
desired principles. But this is just the kind of supply 
which a prudent investigator is most chary of granting 
either to himself or others. For its misuse undermines 
the foundations of science, and involves in common dis- 
credit illusory theories and legitimate schemes of inductive 
reasoning. 
It is not without cause that solar physicists have 
adopted what M Schulz calls the “ gas-ball theory” of 
the solar constitution. A mainly liquid sun is for many 
reasons inadmissible. Ata temperature of 10,000° C. and 
upwards, to begin with, no substance known to us upon 
the earth can exist otherwise than in a state of vapour. 
Hence the necessity for having recourse to unknown ele- 
ments with preternaturally high boiling-points. But a 
theory of Nature built upon the unknown has, it must be 
admitted, no very secure basis. Further, the internal 
stores of heat of a liquid sun could not be made available 
at the surface. The heterogeneous materials presumably 
composing it would necessarily arrange themselves, in the 
order of their specific gravities, into a succession of shells. 
growing in density towards the centre, which no possible 
convection-currents would have power to disturb. The 
result would be the formation of a crust, and—so far as 
we can see—the speedy and final cessation of the radia- 
tive function of our luminary. 
Some of the points touched upon by M. Schulz are of 
great interest, and we cannot but feel grateful to him for 
emphasising them, however little we agree with his 
methods of elucidation. He shows, for instance, that an 
atmosphere of hydrogen could not, on any probable 
assumption as to temperature, extend much more than 
