ASTRONOMY AND METEOROLOGY. 339 



qucncc of its greater surface as compared with its solid contents ; 

 hence the 1 moon would have become solid long before the earth, and 

 would oiler for our contemplation an object of immense antiquity, the 

 surface of which, from the absence of air and water, would have 

 undergone no disintegration or change for millions of ages. 



The present condition of the moon's surface seems in great part 

 made up of craters of extinct volcanoes, some 28 miles in diameter. 

 Some of the volcanic mountains of the moon are 28,000 feet high. 

 These are brightly illuminated on one side by the sun ; and from the 

 absence of dill'used daylight, owing to the want of an atmosphere, 

 the further side is in shadow of intense blackness ; and from the same 

 cause, the sky, as seen from the moon, would appear perfectly dark, 

 the stars being always visible. 



The day in the moon is a fortnight in duration, and during this 

 period the temperature on the illuminated side would probably rise to 

 220 Fahrenheit, or hotter than boiling water. The night would be 

 of equal length, and during this time the heat, from the absence of 

 aqueous vapor and atmosphere, would be radiated freely into space, 

 and the temperature would fall to that of space, viz : to 300 below 

 zero Fahr. The absence of air and water in the moon would render 

 impossible the existence of animal and vegetable life corresponding 

 to that which prevails on our globe. 



The use of the moon, as a satellite of the earth, is usually re- 

 garded as being that of a luminary, but from its variable action this 

 use must be regarded as secondary. Its value as inducing the tides 

 and currents of the ocean is of greater importance, both as conducing 

 to the sanitary condition of the sea, and as aiding transit in rivers, 

 by the ebb and flow of the tide. At the conclusion of the lecture, 

 Mr. Nasmyth illustrated the formation of the radiating cracks on the 

 moon's surface, by congealing water in a thin glass globe hermetically 

 sealed, when it cracked in lines radiating from a single point, the 

 cracks in the moon being attributed to the contraction of its external 

 hardened crust during the period of its rapid congelation. 



