172 



breach, which seems to have been the effect of 

 a flowing of very old lava. We descended 

 through this breacli toward the bottom of the 

 funnel, the figure of which is elliptic. It's great- 

 er axis has a direction from north-west to south- 

 east, nearly N. 35° W. The greatest breadth of 

 the mouth appeared to us to be 300 feet, the 

 smallest 200 feet. These numbers agree very 

 nearly with the measures of Messrs. Verguin, 

 Varela, and Borda % for these travellers assign 

 40 and 30 toises to the two axes -f*. 



It is easy to conceive, that the size of a cra- 

 ter does not depend solely on the height and 

 mass of the mountain, of which it forms the 

 principal air vent. This opening is indeed sel- 

 dom in direct ratio with the intensity of the vol- 

 canic fire, or with the activity of the volcano. 

 At Vesuvius, which is but a hill compared with 

 the Peak of TenerifFe, the diameter of the crater 

 is five times greater. When we reflect, that very 

 lofty volcanoes throw out less matter by their 

 summits, than by lateral openings, we should be 

 led to think, that the lower the volcanoes are, 

 their force and activity being the same, the more 



* Voy. de la Flore, t. p. 94. Manusc. du D6p6t de la 

 Marine, cah. 1, p. 15. Voy. de Marchand, t. ii, p. 11. 



t Mr. Cordier, who visited the top of the Peak four years 

 after me, estimates the greater axis at 66 toises (Journ. de 

 Phys. t. lvii. p. 62). Lamanon thinks it 50 toises. But 

 Mr. O'Donnel gives the crater a circumference of 236 toises 

 (550 mras). 



i 



