92 ROUGH WAYS MADE SMOOTH. 



liquid on the moon's surface would find its way. The 

 down-flowing lava would not be included in this description, 

 as being rather viscous than liquid ; but if any water 

 existed at that time it would occupy the depressed regions 

 which at the present time are called Maria or Seas. 



It is a question of some interest, and one on which dif- 

 ferent opinions have been entertained, whether the moon 

 at any stage of its existence had oceans and an atmo- 

 sphere corresponding in relative extent to those of the 

 earth. It appears to me that, apart from all the other 

 considerations which have been suggested in support of the 

 view that the moon formerly had oceans and an atmosphere, 

 it is exceedingly difficult to imagine how, under any circum- 

 stances, a globe so large as the moon could have been 

 formed under conditions not altogether unlike, as we sup- 

 pose, those under which the earth was formed (having a 

 similar origin, and presumably constructed of the same 

 elements), without having oceans and an atmosphere of 

 considerable extent. The atmosphere would not consist of 

 oxygen and nitrogen only or chiefly, any more than, in all 

 probability, the primeval atmosphere of our own earth was 

 so constituted. We may adopt some such view of the 

 moon's atmosphere mutatis mutandis as Dr. Sterry Hunt 

 has adopted respecting the ancient atmosphere of the earth. 

 Hunt, it will be remembered, bases his opinion on the 

 former condition of the earth by conceiving an intense heat 

 applied to the earth as now existing, and inferring the 

 chemical results. ' To the chemist,' he remarks, 'it is 

 evident that from such a process applied to our globe would 

 result the oxidation of all carbonaceous matter ; the con- 

 version of all carbonates, chlorides, and sulphates into 

 silicates ; and the separation of the carbon, chlorine, and 



of the triangle having Copernicus, Aristarchus, and Kepler at its angles 

 (or more exactly between Milichius and Bessarion) is lower than the 

 surface around Hortensius (between Copernicus and Kepler), but not 

 so low as the Mare Imbrium, far away from the region of ray centres of 

 which Copernicus, Aristarchus, and Kepler are the principal. 



