56 SCIENCE IN SHORT CHAPTERS. 



towards the spectator than does the general convex lunar 

 surface, and thus they become especially visible at the full 

 Moon. 



Such foldings and fractures would occur after the subsi- 

 dence and solidification of the lava-forming liquid that is, 

 when the formation of new craters had ceased in any given 

 region; hence they would extend across the minor lateral 

 craters formed by outbursts from the sides of the main 

 cone, in the manner actually observed. 



The fact that the bottoms of the great walled craters of 

 the Moon are generally lower than the surrounding plains 

 must not be forgotten in connection with this explanation. 



I will not venture farther with the speculations suggested 

 by the above-described resemblances, as my knowledge of 

 the details of the telescopic appearances of the Moon is but 

 second-hand. I have little doubt, however, that observers 

 who have the privilege of direct familiarity with such de- 

 tails, will find that the phenomena presented by the cooling 

 of iron cinder, or other fused silicates, are worthy of 

 further and more careful study. 



NOTE ON THE DIEEOT EFFECT OF SUN-SPOTS 

 ON TERRESTRIAL CLIMATES. 



PKOFESSOR LABTGLEY determines quantitatively the ef- 

 fects respectively produced by the radiations from the solar 

 spots, penumbra, and photosphere upon the face of a ther- 

 mopile, and infers that these effects measure their relative 

 influence on terrestrial climate. 



In thus assuming that the heat communicated to the 

 thermopile measures the solar contribution to terrestrial 

 climate, Professor Langley omits an important factor, viz., 

 the amount of heat absorbed in traversing the earth's 

 atmosphere; and in measuring the relative efficiency of the 

 spots, penumbra, and photosphere, he has not taken into 

 account the variations of diathermancy of the intervening 



