THE ORIGIK OF LUKAR VOLCANOES. 105 



and oxides of iron, alumina, manganese, etc. The cinder 

 separated from this iron displayed the phenomena above 

 described very remarkably, and jets of yellowish flame were 

 thrown up from the craters while the lava was flowing. The 

 flame was succeeded by dense white vapors as the temperature 

 of the cindor lowered, and a deposit of snow-like, flocculent 

 crystals was left upon and around the mouth or crater of each 

 cone. The miniature representation of cosmical eruptions was 

 thus rendered still more striking, even to the white deposit of 

 the haloid salts which Palmier! has described as remaining 

 after the recent eruption of Vesuvius. 



The gases thus evolved have not yet been analytically 

 examined, and the details of the powerful reactions displayed 

 in this process still demand further study ; but there can be 

 no doubt that the combination of silicic acid with the base of 

 the fluorspar is the fundamental reaction to which the evolu- 

 tion of the volatile fluorides, etc., is mainly due. 



A corresponding evolution of gases takes place in cosmical 

 volcanic action, whenever silicic acid is fused in contact with 

 limestone or other carbonate, and a still closer analogy is pre- 

 sented by the fusion of silicates in contact with chlorides and 

 oxides, in the absence of water. If the composition of the 

 Moon is similar to that of the Earth, chlorides of sodium, etc. 

 must form an important part of its solid crust ; they should 

 correspond in quantity to the great deposit of such salts that 

 would be left behind if the ocean of the Earth were evaporat- 

 ed to dryness. The only assumptions demanded in applying 

 these facts to the explanation of the surface configuration of 

 the Moon are, 1st, that our satellite resembles its primary in 

 chemical composition ; 2d, that it has cooled down from a 

 state of fusion ; and 3d, that the magnitude of the eruptions, 

 due to such fusion and cooling, must bear some relation to the 

 quantity of matter in action. 



The first and second are so commonly made arid understood, 

 that I need not here repeat the well-known arguments upon 

 which they are supported, but may remark that the facts above 

 described afford new and weighty evidence in their favor. 



If the correspondence between the form of a freely sus- 

 pended and rotating drop of liquid and that of a planet or 

 satellite is accepted as evidence of the exertion of the same 

 forces of cohesion, etc. on both, the correspondence between 

 the configuration of the lunar surface, and that of small quan- 

 tities of fused and freely cooled earth-crust matter, should at 



