12 KANSAS ACADEMY OF SCIENCE. 
by the Moen. Yet it is fair to assume that the ‘‘ meteoric theory ”’ is true as one 
of the factors in any lunar theory that may be advanced. The volcanic is also 
another factor that must be considered as equally important. There is, there- 
fore, no objection to the statement that both forms of action, the voleanic and 
the impact of meteors, may have had each its due share in bringing about the 
present condition of the Moon’s surface. 
The third or ‘‘ tidal theory’’ supposes a time when ie Moon was liquid but 
covered with a thin crust. ‘‘The Moon then rotated more rapidly than now, and 
great tides, excited by the Earth’s attraction, rocked and cracked its crust, and 
here and there squeezed out a portion of the liquid nucleus, which flowed back 
again when the tidal wave had passed ; but congelation caught the flood at its 
edges, so as to mark its limit by asolid ridge. By each successive tide the opera- 
tion was repeated, with the result that the wall was given a circular form and 
was gradually built up. The process was finally closed by the congelation of 
lava in the orifice, and while the congelation was in progress the last feeble 
eruption sometimes produced a central hill.’”? The tidal theory is quite strong in 
certain directions, while in others it is weak. 
I now desire to pass by these three forms or theories, and construct another 
which may or may not have merit of its own; asystem of lunar dynamics, which, 
so far as I know, has never been looked at in the light in which I now propose to 
consider it. The suggestion is pertinent right here, that this fourth theory does 
not leave out of sight the other three as factors of importance in the solution of 
the problem in hand. 
After the Moon had collected her material together into the form of a globular 
mass, and before becoming a rigid body as it is now known to be, that is when 
still a gaseous or liquid body, there is scarcely a doubt as to the existence of a 
force within the Moon powerful enough to produce each and all the peculiar 
markings on the lunar surface. The most important member of the solar system, 
the Sun, is in either a gaseous or liquid"state, and has been so for millions of 
years, and will continue to be so for millions of years more. During all these 
years the sun has been, and will continue to be, diminishing in size at the rate of 
about 250 feet in diameter per year. The annual contraction of the Sun’s mass 
will in time not only solidify the Sun, but diminish very rapidly toward the end 
the amount of heat given off. Finally, the condition of the Sun may become that 
of a cold, dark body, destitute of both heat and light, and if there be no atmos- 
phere and aqueous vapor such as we are acquainted with, then the solar surface 
will present an appearance similar to that of the Moon—a surface covered with 
mountain ranges and peaks, craters, fissures, and streaks. But if an atmosphere 
and aqueous vapor should be in existence at that remote time of the future, then 
surface markings resembling those of the earth will.characterize the surface of 
the Sun. 
The contraction of the Sun at the rate of 250 feet*per annum is sufficient, ac- 
cording to the theory of celestial dynamics, to producetall the heat the sun now 
gives off, and moreover is enough for that purpose until the Sun is diminished to 
the size of a body sensibly smaller than now. This contraction of the Sun and 
the consequent radiation of heat may in part be the form of energy, or one of the 
forms of energy, in operation upon and within the Sun, to which the sun-spots 
owe their origin. Sun-spots range in diameter from 500 to 100,090 miles or even 
more, and the penumbra is still greater. As to their depth, they seldom exceed 
2,500 miles, although in one instance, observed by Mr. Langley, the enormous 
depth of 5,000 miles was probably reached. 
The force, or forces, at work upon and within the Sun will, after the lapse of 
