TRANSACTIONS OF THE SECTIONS. 25 
going results would require that the periods of geological time should be immense 
compared to those of history. It is also evident that the explanation of the former 
high temperature at the earth’s surface would more than ever require the hypothesis 
of its having been once in a state of fusion. 
—_- —_—— 
On the Structure of the Lunar Surface and its relation to that of the Earth. 
By James NASMYTH. 
The subject was illustrated by a series of drawings which the author has executed 
by the aid of a powerful telescope, which he has made for himself for the express 
purpose of following up his investigations on the subject in question. These appear, 
from the drawings exhibited and the description given by Mr. Nasmyth, to afford 
striking illustrations of the nature and action of some of those agencies which in 
remote periods of the earth’s geological history has given to its surface many of its 
most remarkable features; namely, as to the causes of volcanic action, the protrusion 
of igneous rocks, the upheaving of mountain ranges, as well as the submersion of ex- 
tensive portions of the earth’s surface, all of which vast geological phenomena Mr. 
Nasmyth appears to assign to a few grand and simple prime causes, resulting from 
the consolidation and alternate contraction of the crust and interior of the earth or 
moon, both of which planets appear to have originally been in a molten condition. 
After drawing attention to the vast number and magnitude of crater-formed moun- 
tains with which every portion of the moon’s surface appears to be covered, Mr. 
Nasmyth proceeded to give the reasons for the conclusion that these crater-formed 
mountains are really the craters of extinct lunar volcanos; pointing out the frequent 
occurrence of the:central cone, the result of the last eruptive efforts of an expiring 
volcano, a feature familiar to all those who have observed volcanic craters on the 
earth’s surface. This central cone Mr. Nasmyth showed to exist in the majority of 
the lunar craters, and thereby drew the conclusion that they were the result of the 
same kind of action which has produced craters on the volcanos of the earth. 
The cause of the vast numbers of such volcanic mountains with which the lunar 
surface is bespattered was next considered, and traced to the rapid consolidation and 
contraction of the crust of the moon, whose mass or bulk being only ;th of that of 
the earth, while its surface is the τεῦ, has in consequence of these proportions a 
-radiating or heat-dispensing surface four times greater than that of the earth in rela- 
tion to its bulk. From this simple geometrical consideration Mr. Nasmyth explained 
how it was that, by the rapid cooling and collapse of the crust of the moon on its 
molten interior, the fluid matter under the solid crust was by this “‘ hide-binding ” 
action forced to find an escape through the superincumbent solid crust and come 
forth in the great volcanic actions which in some remote period of time have covered 
its surface with those myriads of craters and volcanic features that give to its surface 
its remarkable character. 
The cause of the vast magnitude of the lunar craters was next alluded to, and 
assigned, ‘as in the former case, to the rapid and energetic collapse of the moon’s 
crust on its yet molten interior. The action as regards the wide dispersion of the 
ejected matter was enhanced by the lightness of the erupted matter, the force of gravity 
which gives the quality of weight to matter on the moon as on the earth being very 
much less on the surface of the moon than on the earth, so that the collapse action 
had to operate on material probably not half the weight of cork bulk for bulk. 
The causes of those vast ranges of mountains seen on the moon’s surface were next 
touched on; and Mr. Nasmyth endeavoured to explain them by the continued pro- 
gress of the collapse action of the solid crust of the moon crushing down or following 
the contracting molten interior, which by the gradual dispersion of its heat would 
retreat from contact with the interior of the solid crust, and permit that to crush 
down and so force that portion of the original surface out of the way, and in conse- 
quence of this action assume the form and arrangement of mountain ranges. Mr. 
Nasmyth, in illustration of this important action, adduced the familiar case of the 
wrinkling of the surface of an apple, by reason of the contraction of the interior, and 
the inability of the surface to accommodate itself to the change otherwise. The 
mountain ranges in question Mr. Nasmyth considers to be nothing more or less than 
