330 COSMOS. 



from the volcanoes of Quito. The Journal d'uti Voyage en 

 Italie, which was read at the meeting of the 20th April, 

 1757, only appeared in 1762 in the Memoires of the Aca- 

 demy of Paris, and is of some geognostic importance in the 

 history of the recognition of old extinct volcanoes in France, 

 because in this journal, La Condamine, with his peculiar 

 acuteness, and without knowing of the certainly earlier ob- 

 servations of Guettard, 23 expresses himself very decidedly 

 upon the existence of ancient crater-lakes and extinct vol- 

 canoes in middle and northern Italy and in the south 

 of France. 



This remarkable contrast between the narrow and un- 

 doubted lava-streams of Auvergne thus early recognized, 

 and the often too absolutely asserted absence of any effusion 

 of lava in the Cordilleras, occupied me seriously during the 

 whole period of my expedition. All my journals are full of 

 considerations upon this problem, the solution of which I 

 long sought in the absolute elevation of the summits and in 

 the vastness of the circumvallation, that is to say, the sink- 

 ing of trachytic conical mountains from mountain-plains of 

 eight or nine thousand (85009600 English) feet in eleva- 

 tion and of great breadth. We now know, however, that a 

 volcano of Quito, 17,000 feet in height, which throws out 

 scoriae (that of Macas), is uninterruptedly much more 

 active than the low volcanoes Izaleo and Stromboli; we 

 know that the eastern dome-shaped and conical mountains, 

 Antisana and Sangay, have free slopes towards the plains of 

 the Napo and Pastaza ; and the western ones, Pichincha, 

 Iliniza, and Chimborazo, towards the affluents of the Pacific 

 Ocean. In many also the upper part projects without cir- 

 cumvallation eight or nine thousand feet above the elevated 

 plateaux. Moreover, all these elevations above the sea-level, 

 which is regarded, although not quite correctly, as the mean 

 elevation of the earth's surface, are certainly inconsiderable 

 as compared with the depth which we may assume to be 

 that of the seat of volcanic activity, and of the necessary 

 temperature for the fusion of rock-masses. 



23 Guettard's memoir on the extinct volcanoes was read at the 

 Academy in 1752, consequently three years before La Condamine's 

 journey into Italy; but only printed in 1756, consequently during the 

 Italian travels of the astronomer. 



