Review of Recent Geoloi/ical Literature. 185 
of chemical elements once compounded, ret|uires more heat tlian the 
interstellar spaces posaeas. Attenuation may favor such decomposi- 
tion, but the re(iuiaite dejjree of heat is totally wanting. (c) The 
degree of heat in the sun is too Rreat to allow the chemiciil association 
of the wases that this theory 8ui)poses are continually falling ujion its 
polar regions. The falling gases wouUl cool the sun rather than heat 
it. (d) Jlie chemical composition at the poles, supposed by this 
theory, evolves, of course, exactly tlie same amount of heat as that 
required for the decomposition of the same substances on their equa- 
torial flight from the sun, and thus adds no heat to the sun, and hence 
can not supply the enormous radiation, to account for which '\s the 
problem to be solved. (o) "If the vigorous logic of mathematics 
would admit of matter being without weight, or even weighing less 
than nothing at the sun's equator, so that it would actually leave the 
sun for extended journeys through space, this condition would apf»ly 
to all the equatorial matter of the sun, and, through this, to the whole 
body, which is generally regarded as gaseous. AVe should then have 
the sun himself going abroad in searcli of fuel to maintain the solar 
fires." (f) According to the reasoning of R. A. Proctor (Eclectic, July, 
1882) "there is not the slightest possibility of matter being projected 
into space from the sun's surface by centrifugal tendency,'' yet this 
tendency for gaseous compounds is the corner stone of Dr. Sieman's 
ingenious theory. 
Seventh. Thompson's theory of convection currents. This postulates 
an internal circulation in the fluid of which the sun is supposed to 
consist, through which it is kept of nearly uniform temperature con- 
stantly. The cooled or partially cooled surface is immediately replen- 
ished by currents from within bringing fresh supplies of heat. This 
does not i)rofess to supply an indefinite amount of heat, but .illows of 
the loss of all radiated heat. It depend-^ on the vastness of the heated 
sun, to furnish heat for so long a period that to our apprehension the 
slowness of the change is such that the change is not perceptible. 
This must fail if either of the following propositions be true. Ist. If 
we have sufficient evidence on which to decide that the sun is not 
cooling at all. 2nd. If the lieat given out by the sun is out of all pro- 
portion to the gradual cooling supposed by this theory. The author 
then considers each of these propositions under the caption. Enormous 
amount of heat emitted lnj the sun, and shows conclusively, by quotations 
from Dr. J. R. Mayer, Prof. Young and Prof. Langley, not only that 
the radiation is enormous but that it is .^o vast that it would certainly 
be perceptible, without having areplenishment, within tlie 5,000 years 
that the sun's heat has been observed, amounting to !),000 degrees 
centigrade. This destroys the theory, since it establishes the second 
proposition and strongly fortifies the first. 
THE -Wthor's theory of bol.ar he.xt. 
Having shown the inadequacy of the principal existing theories the 
author considers himself justified in ofll'ering another. "If the theories 
examined are as unsatisfactory to the reader as to the writer, there 
