meunier: theory of volcanoes 649 



ization, revealed to us by the science of comparative anatomy, 

 are an earnest of those which we may discover in regard to the 

 economy of the celestial bodies as a result of the progress of com- 

 parative geology. We know that astronomy proceeds not only 

 by purely morphologic investigations of the celestial bodies, but 

 that several other means of study have been opened to it suc- 

 cessively by physics and chemistry; spectroscopy, which is 

 based on the prismatic analysis of the light emanating from the 

 heavenly bodies or reflected by them, has demonstrated the 

 chemical unity of the heavens, just as telescopy had shown 

 their mechanical coordination. On the other hand, through a 

 piece of good luck which no one could have foreseen or hoped 

 for, bits of substance derived from the cosmic regions and pre- 

 cipitated on our planet in the form of meteorites, have supple- 

 mented the spectroscopic evidence by a large number of extra- 

 terrestrial minerals, enabling still closer comparisons to be made. 

 A geologic relationship has thus been revealed, and the legiti- 

 macy of synthetic suppositions of the widest scope can now no 

 longer be called in question. It does seem as if we were now in 

 position to say that all conceptions that hold that the physical 

 constitution of heavenly bodies differs from the constitution of 

 the earth are erroneous. I may be permitted to express the 

 hope that the present paper may serve to reinforce this conclu- 

 sion by showing that the moon, which has inspired so many 

 hypotheses, in reality presents morphologic features that are 

 not only compatible with those of the earth but also harmonize 

 completely with the proposed volcanologic theory of the earth, an 

 agreement as neat as it was unforeseen. It furnishes the most 

 valuable confirmation of that theory, while in return it receives 

 not less decisive confirmation from geologic studies. 



It is a rare pleasure to find such complete agreement between 

 two lines of study which at first sight seem so unrelated. I 

 may even be permitted to express a sort of gratitude, somewhat 

 superstitious perhaps, to the Unknown Cause which reveals to 

 our minds some of the harmonies, hitherto so jealously hidden, 

 of the natural mechanism. A glimpse of these harmonies some- 

 times bursts on the mind so suddenly that one has the feeling of 

 an astonished spectator rather than of an originator. 



