Several hypotheses have been advanced to account for earthquakes. Rogers ascribes them to billowy pulsations in the molten matter upon which the flexible crust of the earth floats. Mallet thinks they may be viewed as an uncompleted effort to establish a volcano. Dana holds that they are occasioned by the folding up of the rocks in the slow process of cooling and consequent contraction of the earth's crust. In this process there would occur enormous fractures to relieve the tension; tilted strata would slip, and caverns give way. All this no doubt takes place; but the sudden, paroxysmal heavings incline us to refer the cause to the same eruptive impulse which makes Vesuvius and Cotopaxi discharge pent-up subterranean vapor and gas. The most destructive earthquakes occur when the overlying rocks do not break and give vent to the imprisoned gas. There is some connection between volcanoes and earthquakes; the former are, to a certain extent, "safety-valves." The column of smoke from the volcano of Pasto suddenly disappeared just before the great earthquake at Riobamba. In the spring of 1868 Pichincha and Cotopaxi showed signs of increasing activity, but in the summer became quiet again. Cotocachí and Sangai, 200 miles apart, were awaked simultaneously; the former, silent for centuries, sent forth dense masses of earth and volcanic matter to a distance of many miles, covering thousands of acres; the latter thundered every half hour instead of hourly, as before. Still, the greatest earthquakes do not occur in the vicinity of active volcanoes. Lisbon and Lima (where, on an average, forty-five shocks occur annually, and two fearful ones in a century) are far distant from any volcanic vent; likewise Northern India, South Africa, Scotland, and the United States.
An earthquake is beyond the reach of calculation. Professor Perrey, of Dijon, France, is endeavoring to prove that there is a periodicity in earthquakes, synchronous with that in the tides of the ocean, the greatest number occurring at the time of new and full moon.[96] If this theory be sustained, we must admit the existence of a vast subterranean sea of lava. But all this is problematical. Earthquakes appear independently of the geology of a country, though the rate of undulation is modified by the mineral structure. Earthquake waves seem to move more rapidly through the comparatively undisturbed beds of the Mississippi Valley than through the contorted strata of Europe. Meteorology is unable to indicate a coming earthquake, for there is no sure prophecy in sultry weather, sirocco wind, and leaden sky. The Lisbon shock came without a warning. Sudden changes of the weather, however, often occur after an earthquake. Since the great convulsion of 1797 the climate of the Valley of Quito is said to be much colder. A heavy rain often follows a violent earthquake in Peru.
No amount of familiarity with earthquakes enables one to laugh during the shock, or even at the subterranean thunders which sound like the clanking of chains in the realm of Pluto. All animated nature is terror-stricken. The horse trembles in his stall; the cow moans a low, melancholy tune; the dog sends forth an unearthly yell; sparrows drop from the trees as if dead; crocodiles leave the trembling bed of the river and run with loud cries into the forest; and man himself becomes bewildered and loses all capacity. When the earth rocks beneath our feet (the motion resembling, in the words of Darwin, "that felt by a person skating over thin ice which bends under the weight of his body"), something besides giddiness is produced. We feel our utter insignificance in the presence of a mysterious power that shakes the Andes like a reed. But more: there is an awful sensation of insecurity. "A moment (says Humboldt) destroys the illusion of a whole life: our deceptive faith in the repose of nature vanishes, and we feel transported, as it were, into a region of unknown destructive forces." A judgment day seems impending, and each moment is an age when one stands on a world convulsed.
[CHAPTER XI.]
"The Province of the Orient," or the Wild Napo Country.— The Napos, Zaparos, and Jívaros Indians.— Preparations to cross the Continent.
On the eastern slope of the Ecuadorian Andes, between the Marañon and its tributary the Putumayo, lies the Napo country. This almost unknown region has the area of New York and New England together. The government of Quito, by a sonorous decree in 1854, baptized it "La Provincia del Oriente." Peru likewise claims it, but neither republic has done any thing to colonize it. A dense primeval forest, broken only by the rivers, covers the whole territory, and is the home of wild races untouched by civilization.[97] There is not a road in the whole province. A footpath, open only in the dry season, and barely passable then, connects Quito and the Rio Napo. Congress lately promised to put Canélos in communication with the capital; but the largest villages in this vast and fertile region—Archidona, Canélos, and Macás—still remain isolated from the outer world.[98] Ecuador once appointed a functionary under the high-sounding title of "Governor of the Orient," with a salary of $700; but now the Indians are not troubled with any higher official than an alcalde.
The country is very thinly inhabited. The chief tribes are the semi-Christianized Napos (sometimes called Quijos), dwelling on the north bank of the Napo; the peaceful but uncivilized Zaparos, living between the Napo and Pastassa, and the warlike Jívaros, spread over the unexplored region between the Pastassa and Santiago.
These oriental tribes would probably be assigned by D'Orbigny to the Antisian branch of the Alpine races of South America. Dwelling amid the darkness of primeval forests, and on the gloomy banks of mountain torrents, they have acquired modifications of character, physical and moral, which distinguish them from the natives of the high and open regions, or the steaming lowlands of the Amazon. In color, however, they do not appear to us to be entitled to the name of "white men;" they approach nearer to the bronze complexion of the Quichuans than the yellow cast of the Brazilians. We see no evidence of that "bleaching process" resulting from a life under the dense canopy of foliage of which the learned French naturalist speaks, neither did we perceive the force of his statement that the color of the South American bears a very decided relation to the humidity of the atmosphere.