1859.] SCROPE CONES AND CKATERS. 533 



MM. E. de Beaumont and Dufrenoy have applied their upheaval- 

 theory to the great volcanic mountains of Central France, the Mont 

 Dore, Cantal, and Mezen. Being well acquainted with these districts, 

 which I have revisited in each of the last two years, and re-examined 

 specially with a view to this question, I will venture to assert that 

 the theory is as little justified by the facts, or rather is as inconsistent 

 with them, in these instances, as in those of Teneriife, Etna, or Ve- 

 suvius. We have presented to us in that district the results of a 

 series of subaerial eruptions continued at intervals, from a great many 

 different vents, through several geological periods, commencing with 

 the Lower Miocene, and reaching far into the recent, probably into 

 the human, era. No clear line can be drawn between them in re- 

 spect to age, separating the ancient from the modern rocks, upon 

 grounds of mineral character or constitution. It is from their aspect 

 and position only, that is to say, from the more or less of denudation 

 and decomposition they have evidently suffered through atmospheric 

 agency, that their relative ages are determinable. But these cha- 

 racters of either kind are strongly marked and strikingly demonstra- 

 tive, and moreover correspond together in the most remarkable and 

 unmistakeable manner. The fresh-looking lava-streams that take 

 their rise from perfect cones of loose red scoriae and lapilli, and whose 

 scoriform surfaces scarcely admit as yet of a scanty vegetation, occupy 

 the lowest levels, and for the most part the bottoms of the existing 

 valleys ; while the elongated sheets of basalt or trachyte, whose 

 scorise have either almost disappeared, or been converted into argil- 

 laceous boles, or tuffs stratified by water, appear as high platforms 

 crowning the summits of hills. Still the average angles of inclination 

 of both classes of lavas are the same. Indeed it is common to see a bed 

 of recent lava tilling up the bottom of a narrow vaUey through a course 

 of many miles, while the heights on either side, several hundi-ed feet 

 above it, are crowned by parallel plateaux of basalt, descending with 

 the same inclination, or gradient, in the same direction, from the 

 same heights whence all have evidently been erupted. Kow this 

 fact is of coui'se completely in accordance with the supposition that 

 all derive their inclination simply from having flowed, as lavas, down 

 the surface- slopes on which they rest, the different levels of con- 

 tiguous streams being due to the successive excavation of the valleys 

 occupied by the more recent lavas in the interval between their 

 eruption and that of the adjoining older and higher-placed sheets of 

 basalt. If, however, we are to believe that the latter owe their 

 inclined position to upheaval (which is the doctrine of MM. de Beau- 

 mont and Dufrenoy), it seems impossible to account for the constant 

 uniformity of their slope with that of the parallel lavas which are 

 admitted by these geologists to owe their inclination to fluidity alone. 

 There is, moreover, no line of separation to be drawn between the 

 supposed two classes. 



Nor is there, in this case, room for even the argument (worth- 

 less as it is) drawn by the upheavalists in other instances from the 

 supposed impossibility of lavas consolidating in thick beds at a high 

 angle of elevation ; for the slopes of the Mont Dore and Cantal, com- 



