GEOLOGY. 283 



plains, but, according to my calculations, only 130 feet above the ocean. 

 Unless there is some great error in these data, and I can conceive of 

 none, they would seem to prove that there has been a subsidence of 

 the plain since the almost infinitely remote period when the bed of 

 lava flowed upwards from the depths of the earth. I may mention 

 that in the vicinity of the volcanoes water is scarce, and can only be 

 obtained by digging to great depths. The particular well which I 

 refer to. at a cattle estate eighteen miles northeast of Leon, is up- 

 ward of 300 feet in depth, the water pure, with no saline materials in 

 solution." 



Mr. Squier then goes on to examine the question of a ship-canal, 

 which he considers practicable, and, in conclusion, states that a large 

 bed of semi-bituminous coal, resembling the Mt. Savage coal, has 

 been discovered in San Salvador, on the banks of the River Lempa, 

 about sixty miles from the Gulf of Fonseca. 



THE LUNAR SURFACE AND ITS RELATION TO THAT OF THE 



EARTH. 



MR. NASMYTH read to the British Association, at Edinburgh, a 

 "paper on the above subject, which was illustrated by a series of draw- 

 ings executed by the aid of a powerful telescope. After calling at- 

 tention to the vast number and magnitude of crater-formed mountains, 

 with which every portion of the moon's surface appears to be covered, 

 Mr. N. proceeded to give the reasons for the conclusion that they are 

 really the craters of extinct lunar volcanoes, pointing out the frequent 

 recurrence of the central cone, the result of the last eruptive efforts 

 of an expiring volcano. The cause of the vast number of the lunar 

 volcanoes was traced to the rapid consolidation and contraction of the 

 crust of the moon, whose mass, being but one G4th of that of the earth, 

 while its surface is one 16th, has a radiating surface four times greater 

 than that of the earth in relation to its bulk. In consequence, by the 

 rapid cooling and collapse of the crust of the moon on its molten in- 

 terior, the fluid matter under the solid crust was forced to find an 

 escape through it, and come forth in those vast actions w : hich have 

 produced such numbers of volcanoes. The cause of the vast magni- 

 tude of the lunar craters was also assigned to the rapid and energetic 

 collapse of the moon's crust, the action as regards the wide dispersion 

 of the ejected matter being enhanced by its lightness, which is caused by 

 the much less force of gravity on the lunar than on the terrestrial sur- 

 face, so that the collapse action had to operate on material probably not 

 half the weight of cork, bulk for bulk. The vast ranges of mountains 

 on the moon's surface Mr. Nasmyth explains by the continued progress 

 of the collapse action of the solid crust, crushing down or following 

 the molten interior, which, by the gradual dispersion of its heat, 

 would retreat from contact with the interior of the solid crust, and 

 permit it to crush down, and so force that portion of the original sur- 

 face out of the way, and in consequence assume the form and arrange- 

 ment of mountain ranges. In illustration of this action, Mr. Nasmyth 

 adduced the familiar case of the wrinkling of ths surface of an apple. 



