12 SCIENCE. 
plies: * ‘‘ The well-founded dynamical the- 
ory of the sun’s heat carefully worked out 
and discussed by Helmholtz, Newcomb and 
myself, says No if the consolidation of the 
earth took place as long [ago] as 50 million 
years; the solid earth must in that case 
have waited 20 or 50 [380?] million years 
for the sun to be anything nearly as warm 
as he is at present. If the consolidation of 
the earth was finished 20 or 25 million 
years ago the sun was probably ready, 
though probably not then quite so warm as 
at present, yet warm enough to support 
some kind of vegetable and animal life on 
the earth.”” Here is an unqualified assump- 
tion of the completeness of the Helinholtz- 
ian theory of the sun’s heat and of the cor- 
rectness of deductions drawn from it in re- 
lation to the past life of the sun. There is 
the further assumption, by implication, that 
no other essential factors entered into 
the problem. Are these assumptions be- 
yond legitimate question? In the first 
place, without questioning its correctness, 
is it safe to assume that the Helmholtz- 
ian hypothesis of the heat of the sun is 
a complete theory? Is present knowledge 
relative to the behavior of matter under 
such extraordinary conditions as obtain in 
the interior of the sun sufficiently exhaust- 
ive to warrant the assertion that no unrec. 
ognized sources of heat reside there? What 
the internal constitution of the atoms may 
be is yet an open question. It is not im- 
probable that they are complex organiza- 
tions and the seats of enormous energies. 
Certainly, no careful chemist would affirm 
either that the atoms are really elementary 
or that there may not be locked up in them 
energies of the first order of magnitude. 
No cautious chemist would probably ven- 
ture to assert that the component atome- 
cules, to use a convenient phrase, may not 
have energies of rotation, revolution, posi- 
tion and be otherwise comparable in kind and 
* SCIENCE, May 19, 1899, p. 711. 
[N.S. Vou. X. No. 236. 
proportion to those of a planetary system. 
Nor would he probably feel prepared to af- 
firm or deny that the extraordinary condi- 
tions which reside in the center of the sun 
may not set freea portion of this energy. 
The Helmholtzian theory takes no cog- 
nizance of latent and occluded energies 
of an atomic or ultra-atomic nature. A 
ton of ice and a ton of water at a like dis- 
tance from the center of the system are ac- 
counted equivalents, though they differ no- 
tably in the total sum of their energies. 
The familiar latent and chemical energies 
are, to be sure, negligible quantities com- 
pared with the enormous resources that re- 
side in gravitation. But is it quite safe to 
assume that this is true of the unknown 
energies wrapped up in the internal consti- 
tution of the atoms? Are we quite sure 
we have yet probed the bottom of the 
sources of energy and are able to measure 
even roughly its sum-total ? 
There are some things hereabouts in the 
instruction we receive that puzzle us with 
our geological limitations : 
1. We are taught that there is a certain 
critical temperature for every substance 
above which it takes the gaseous form, and 
no amount of pressure can reduce it to the 
liquid or solid state. 
2. We are taught that gases are compres- 
sible to an indefinite extent provided their 
temperatures be above the critical point. 
3. We are told the temperature of the 
interior of the sun is probably above the 
critical temperature of any known sub- 
stance, and hence that all the material of 
the interior of the sun is probably gaseous. 
4. Weare taught that so long as the sub- 
stances of the sun remain in the gaseous 
condition the temperature of the sun must 
rise from increased self-compression. It 
cannot, therefore, fall to the critical tem- 
perature of the component substances, and 
must, therefore, continue in the gaseous 
state and grow hotter and hotter. 
