211 



likened, except " craters of elevation." The Cantal and the Mon- 

 tagnes d'Oisans, however, appear to be the ruin or debris of very 

 similar objects. 



3. For the most part, the disposition of these craters is irregular 

 and capricious ; but, in a number of instances, sufficiently consider- 

 able to indicate the operation of lata, we find rows of small craters, 

 close to each other, arranged almost in a straight line. This ar- 

 rangement is perhaps a clue to two phenomena. First, Were the 

 craters a little closer, a longitudinal portion of the moon's surface 

 would be blown out, and a furrow would result, exactly like those 

 curious furrows or ditches, which have often puzzled moon-explorers. 

 Secondly, Had the seat of the disturbance been somewhat deep- 

 er, or the disturbing force somewhat weaker, a mere rectilinear 

 elevation would have ensued, — a serrated chain of mountains. 



Generalizing on these phenomena. Professor Nichol suggests that 

 the following conclusions may be safely hazarded. 



I. The forms of the moon give decided countenance to the theory 

 of elevation craters, developed by Von Buch and De Beaumont, as 

 at least one modus operandi of the upheaving cause. It even ap- 

 pears to be the leading or fundamental one. 



II. The doctrine of the central heat derives no support from 

 these phenomena. Tlie irregular distribution of the craters is not 

 favourable to the idea of any central or general action ; and the 

 limited sphere of the disturbance connected with them, demonstrates 

 that their source is superficial. They rather appear as the clearing 

 out of local deflagrating forces, whose seat is between the two outer- 

 most shells of the moon's body. 



III. The hypothesis of secular refrigeration is, according to the 

 author, discredited by the survey of lunar phenomena. This hy- 

 pothesis was formed upon the idea, that elevations are generally 

 linear, and along great circles of the sphere ; whereas iu the moon, 

 linear elevations are the exception. 



IV. The moon enables us to eliminate a number of non-essential 

 circumstances, from the ultimate problem of the upheaving cause. 

 For instance, the theory lately promulged by Sir John Herschel 

 relative to the dependence of convulsion and elevation upon abra- 

 sion and stratification, according to the author, will not stand good. 

 Considering that the temperature of the earth increases with its 

 depth, in so far as we have yet descended, it is undoubted that 

 abrasion and stratification will cause changes of temperature among 

 the inferior rocks, and therefore expansions, fractures, and exten- 



