VOLCANOES. 



69 



similar zones, is still the same ; so do we ev- 

 erywhere observe the same laws of formation 

 proclaiming themselves in the realm of inor- 

 ganic nature, laws according to which the 

 strata of the crust of the earth stand in a cer- 

 tain relationship to one another, under the in- 

 fluence of elastic forces, and break through one 

 another as dykes. This recurrence of the same 

 phenomena is particularly striking in volcanoes. 

 When the navigator, among the islands of dis- 

 tant seas, finds himself surrounded by palms 

 and strange forms of vegetation, and no longer 

 sees the same stars, in the individualities of 

 the landscape he still traces Vesuvius, the 

 dome-shaped summit of Auvergne, the craters 

 of elevation of the Canaries and Azores, the 

 fissures of eruption of Iceland repeated and re- 

 flected ; a glance at the attendant of our planet, 

 the moon, generalizes still farther the analogy 

 of formation here adverted to. In the maps of 

 the moon, drawn from the image reflected in 

 powerful telescopes, in our satellite, without 

 atmosphere and without water, we can distin- 

 guish vast craters of elevation, which surround 

 conical mountains, or support them on their 

 circular walls : unquestionable effects of the 

 reaction of the interior of the moon upon her 

 exterior, aided by the influence of diminished 

 gravity. 



If in many languages volcanoes are very 

 properly designated Burning Mountains, it 

 would still be a great mistake to suppose that 

 they were produced by any gradual accumula- 

 tion of the streams of lava that have flowed 

 from them ; their origin appears to be much 

 more generally the consequence of a sudden 

 upheaval of tenacious masses of trachyte or 

 augitic rock, including Labrador spar. The 

 measure of the upheaving force reveals itself 

 in the height of the volcano ; and this is so dif- 

 ferent, that in one case it is a mere hillock (as 

 in Cosima, one of the Japanese Kuriles), in an- 

 other it is a cone that rises to a clear elevation 

 of 18,000 feet. It has seemed to me as if the 

 relative height had a great influence upon the 

 frequency of the eruptions ; as if these were 

 much more common in the lower than in the 

 loftier volcanoes. I will call attention to the 

 following series: Stromboli (2,175 feet high), 

 Guacamayo, in the province of Quiros, which 

 thunders almost every day (I have frequently 

 heard it in Chillo, near Quito, at a distance of 

 22 miles), Vesuvius (3,637 feet high), ^tna 

 (10,200 feet high), the Peake of Tenerifle 

 (11,424 feet high), and Cotopaxi (17,892 feet 

 high). If the focus of these several volcanoes 

 be at the same depth below the surface, a great- 

 er force will be required to raise the molten 

 masses to a 6 or 8 times higher level. Whilst 

 the lowly Stromboli (Strongyle) has laboured 

 restlessly, at least since the times of the Ho- 

 meric traditions, and serves as a light-house 

 to the Tyrrhenian Sea, guiding the seaman with 

 its fiery signal on his course, the more lofty 

 volcanoes are characterized by lengthened pe- 

 riods of repose. The eruptions of the greater 

 number of the colossal volcanoes that crown 

 the Andes, occur at intervals almost of a cen- 

 tury apart : where exceptions to this rule have 

 been observed — and I long ago directed atten- 

 tion to them — they may probably be connected 

 with the circumstance, that the communication 



between the volcanic focus and the crater Oi 

 eruption is not, cannot be conceived to be, 

 equally or permanently free in every volcano 

 at all times. In the less elevated volcanoes 

 the channel of communication may be closed 

 for a season ; so that their eruptions become 

 rarer, without their being, on this account, any 

 nearer to extinction. 



With the consideration of the relation be- 

 tween the absolute heights of volcanoes and 

 the frequency of their activity, in so far as 

 this is externally visible, the place at which 

 the lava flows out is closely connected. Erup- 

 tions from the crater are extremely rare in the 

 case of many volcanoes ; they generally occur 

 from lateral fissures (as noticed by the celebra- 

 ted historian, Bembo, in the 16th century, whilst 

 yet a youth), at places where the flanks of the 

 uplifted mountain, in consequence of their for- 

 mation and inclination, offer the least amount 

 of resistance(^^*). Upon these fissures cones 

 of eruption are occasionally raised. The larger 

 of these are of such dimensions that they are 

 often erroneously designated by the title of new 

 volcanoes ; ranked side by side, they show the 

 direction of a fissure which has again become 

 closed ; the smaller ones frequently occur in 

 groups, thickly set together, and cover whole 

 districts, as it were with bell-shaped, or bee- 

 hive like, elevations. To the latter class be- 

 long the hornitos of Jorullo(^^^), and the cone of 

 eruption of Vesuvius of October, 1822, of the 

 volcano of Awatscha, according to Postels, 

 and of the lava field near the Baidare mount- 

 ains, in the peninsula of Kamtschatka, accord- 

 ing to Erman. 



When volcanoes do not rise free and isola- 

 ted from a plain, when, on the contrary, they 

 are surrounded by table-lands from 9 to 12,000 

 feet high, as in the double chain of the Andes 

 of Quito, this circumstance may very well give 

 rise to the fact, that the most violent eruptions, 

 when red-hot ashes and scoriae are thrown out 

 with detonations that are heard for hundreds 

 of miles around, are never accompanied with 

 streams of lava''^^*). This is the case with 

 the volcanoes of Popayan, of the lofty plains of 

 Los Pastes, and of the Andes of Quito ; the 

 single volcano of Antesana, among the latter, 

 perhaps excepted. 



The height of the cone of ashes, and the di- 

 mensions and form of the crater, are the ele- 

 ments in the figure of volcanoes which more 

 particularly impress upon each of them an in- 

 dividual character; but both of these elements, 

 both the cone and the crater, are perfectly in- 

 dependent of the magnitude of the whole mount- 

 ain. Vesuvius is not one-third of the height of 

 the Peake of TeneriflTe, yet its cone of ashes 

 forms one-third of the whole height of the 

 mountain, whilst the cone of the Peake is only 

 one twenty-second of the entire elevation. In 

 the case of another volcano of much greater 

 height than the Peake, that of Rucu-Pichincha, 

 namely, the relations come nearer to those of 

 Vesuvius. Of all the volcanoes which I have 

 seen in either hemisphere, Cotopaxi is that of 

 which the conical form is the most regular and 

 beautiful. A sudden melting of the snow of 

 its ashy cone indicates the proximity of an 

 eruption. Before there is even any smoke 

 visible in the thin strata of the atmosphere 



