CHAPTER EIGHTEEN.
GEOGRAPHY AND GEOLOGY.
We rested above an hour in the cool shade, while our horses refreshedthemselves on the "grama" that grew luxuriantly around. We conversedabout the singular region in which we were travelling; singular in itsgeography, its geology, its botany, and its history; singular in allrespects.
I am a traveller, as I might say, by profession. I felt an interest inlearning something of the wild countries that stretched for hundreds ofmiles around us; and I knew there was no man living so capable of beingmy informant as he with whom I then conversed.
My journey down the river had made me but little acquainted with itsfeatures. At that time, as I have already related, there was fever uponme; and my memory of objects was as though I had encountered them insome distorted dream.
My brain was now clear; and the scenes through which we were passing--here soft and south-like, there wild, barren, and picturesque--forciblyimpressed my imagination.
The knowledge, too, that parts of this region had once been inhabited bythe followers of Cortez, as many a ruin testified; that it had beensurrendered back to its ancient and savage lords, and the inference thatthis surrender had been brought about by the enactment of many a tragicscene, induced a train of romantic thought, which yearned forgratification in an acquaintance with the realities that gave rise toit.
Seguin was communicative. His spirits were high. His hopes werebuoyant. The prospect of again embracing his long-lost child imbuedhim, as it were, with new life. He had not, he said, felt so happy formany years.
"It is true," said he, in answer to a question I had put, "there islittle known of this whole region, beyond the boundaries of the Mexicansettlements. They who once had the opportunity of recording itsgeographical features have left the task undone. They were too busy inthe search for gold; and their weak descendants, as you see, are toobusy in robbing one another to care for aught else. They know nothingof the country beyond their own borders; and these are every daycontracting upon them. All they know of it is the fact that thence cometheir enemies, whom they dread, as children do ghosts or wolves."
"We are now," continued Seguin, "near the centre of the continent, inthe very heart of the American Sahara."
"But," said I, interrupting him, "we cannot be more than a day's ridesouth of New Mexico. That is not a desert; it is a cultivated country."
"New Mexico is an oasis, nothing more. The desert is around it forhundreds of miles; nay, in some directions you may travel a thousandmiles from the Del Norte without seeing one fertile spot. New Mexico isan oasis which owes its existence to the irrigating waters of the DelNorte. It is the only settlement of white men from the frontiers of theMississippi to the shores of the Pacific in California. You approachedit by a desert, did you not?"
"Yes; as we ascended from the Mississippi towards the Rocky Mountainsthe country became gradually more sterile. For the last three hundredmiles or so we could scarcely find grass or water for the sustenance ofour animals. But is it thus north and south of the route we travelled?"
"North and south for more than a thousand miles, from the plains ofTexas to the lakes of Canada, along the whole base of the RockyMountains, and half-way to the settlements on the Mississippi, it is atreeless, herbless land."
"To the west of the mountains?"
"Fifteen hundred miles of desert; that is its length, by at least halfas many miles of breadth. The country to the west is of a differentcharacter. It is more broken in its outlines, more mountainous, and ifpossible more sterile in its aspect. The volcanic fires have been moreactive there; and though that may have been thousands of years ago, theigneous rocks in many places look as if freshly upheaved. Novegetation, no climatic action has sensibly changed the hues of the lavaand scoriae that in some places cover the plains for miles. I say noclimatic action, for there is but little of that in this centralregion."
"I do not understand you."
"What I mean is, that there is but little atmospheric change. It is butone uniform drought; it is seldom tempestuous or rainy. I know somedistricts where a drop of rain has not fallen for years."
"And can you account for that phenomenon?"
"I have my theory. It may not satisfy the learned meteorologist, but Iwill offer it to you."
I listened with attention, for I knew that my companion was a man ofscience, as of experience and observation, and subjects of the characterof those about which we conversed had always possessed great interestfor me. He continued--
"There can be no rain without vapour in the air. There can be no vapourin the air without water on the earth below to produce it. Here thereis no great body of water.
"Nor can there be. The whole region of the desert is upheaved--anelevated table-land. We are now nearly six thousand feet above sealevel. Hence its springs are few; and by hydraulic law must be fed byits own waters, or those of some region still more elevated, which doesnot exist on the continent.
"Could I create vast seas in this region, walled in by the loftymountains that traverse it--and such seas existed coeval with itsformation; could I create those seas without giving them an outlet, noteven allowing the smallest rill to drain them, in process of time theywould empty themselves into the ocean, and leave everything as it nowis, a desert."
"But how? by evaporation?"
"On the contrary, the absence of evaporation would be the cause of theirdrainage. I believe it has been so already."
"I cannot understand that."
"It is simply thus: this region possesses, as we have said, greatelevation; consequently a cool atmosphere, and a much less evaporatingpower than that which draws up the water of the ocean. Now, there wouldbe an interchange of vapour between the ocean and these elevated seas,by means of winds and currents; for it is only by that means that anywater can reach this interior plateau. That interchange would result infavour of the inland seas, by reason of their less evaporation, as wellas from other causes. We have not time, or I could demonstrate such aresult. I beg you will admit it, then, and reason it out at yourleisure."
"I perceive the truth; I perceive it at once."
"What follows, then? These seas would gradually fill up to overflowing.The first little rivulet that trickled forth from their lipping fulnesswould be the signal of their destruction. It would cut its channel overthe ridge of the lofty mountain, tiny at first, but deepening andwidening with each successive shower, until, after many years--ages,centuries, cycles perhaps--a great gap such as this," (here Seguinpointed to the canon), "and the dry plain behind it, would alone existto puzzle the geologist."
"And you think that the plains lying among the Andes and the RockyMountains are the dry beds of seas?"
"I doubt it not; seas formed after the upheaval of the ridges thatbarred them in, formed by rains from the ocean, at first shallow, thendeepening, until they had risen to the level of their mountain barriers;and, as I have described, cut their way back again to the ocean."
"But does not one of these seas still exist?"
"The Great Salt Lake? It does. It lies north-west of us. Not onlyone, but a system of lakes, springs, and rivers, both salt and fresh;and these have no outlet to the ocean. They are barred in by highlandsand mountains, of themselves forming a complete geographical system."
"Does not that destroy your theory?"
"No. The basin in which this phenomenon exists is on a lower level thanmost of the desert plateaux. Its evaporating power is equal to theinflux of its own rivers, and consequently neutralises their effect;that is to say, in its exchange of vapour with the ocean, it gives asmuch as it receives. This arises, not so much from its low elevation asfrom the peculiar dip of the mountains that guide the waters into itsbosom. Place it in a colder position, _ceteris paribus_, and in time itwould cut the canal for its own drainage. So with the Caspian Sea, theAral, and the Dead Sea. No, my friend, the existence of the Salt Lakesupports my theory. Around its shores lies a fertile country, fert
ilefrom the quick returns of its own waters moistening it with rain. Itexists only to a limited extent, and cannot influence the whole regionof the desert, which lies parched and sterile, on account of its greatdistance from the ocean."
"But does not the vapour rising from the ocean float over the desert?"
"It does, as I have said, to some extent, else there would be no rainhere. Sometimes by extraordinary causes, such as high winds, it iscarried into the heart of the continent in large masses. Then we havestorms, and fearful ones too. But, generally, it is only the skirt of acloud, so to speak, that reaches thus far; and that, combined with theproper evaporation of the region itself, that is, from its own springsand rivers, yields all the rain that falls upon it. Great bodies ofvapour, rising from the Pacific and drifting eastward, first impingeupon the coast range, and there deposit their waters; or perhaps theyare more highly-heated, and soaring above the tops of these mountains,travel farther. They will be intercepted a hundred miles farther on bythe loftier ridges of the Sierra Nevada, and carried back, as it were,captive, to the ocean by the streams of the Sacramento and San Joaquim.It is only the skirt of these clouds, as I have termed it, that, soaringstill higher, and escaping the attractive influence of the Nevada,floats on, and falls into the desert region. What then? No sooner hasit fallen than it hurries back to the sea by the Gila and Colorado, torise again and fertilise the slopes of the Nevada; while the fragment ofsome other cloud drifts its scanty supply over the arid uplands of theinterior, to be spent in rain or snow upon the peaks of the RockyMountains. Hence the source of the rivers running east and west, andhence the oases, such as the parks that lie among these mountains.Hence the fertile valleys upon the Del Norte, and other streams thatthinly meander through this central land.
"Vapour-clouds from the Atlantic undergo a similar detention in crossingthe Alleghany range; or, cooling, after having circled a great distanceround the globe, descend into the valleys of the Ohio and Mississippi.From all sides of this great continent, as you approach its centre,fertility declines, and only from the want of water. The soil in manyplaces where there is scarcely a blade of grass to be seen, possessesall the elements of vegetation. So the doctor will tell you; he hasanalysed it."
"Ya, ya! dat ish true," quietly affirmed the doctor.
"There are many oases," continued Seguin; "and where water can be usedto irrigate the soil, luxuriant vegetation is the consequence. You haveobserved this, no doubt, in travelling down the river; and such was thecase in the old Spanish settlements on the Gila."
"But why were these abandoned?" I inquired, never having heard anyreason assigned for the desertion of these once flourishing colonies.
"Why!" echoed Seguin, with a peculiar energy; "why! Unless some otherrace than the Iberian take possession of these lands, the Apache, theNavajo, and the Comanche, the conquered of Cortez and his conquerors,will yet drive the descendants of those very conquerors from the soil ofMexico. Look at Sonora and Chihuahua, half-depopulated! Look at NewMexico; its citizens living by suffrance: living, as it were, to tillthe land and feed the flocks for the support of their own enemies, wholevy their blackmail by the year! But, come; the sun tells us we muston. Come!
"Mount! we can go through," continued he. "There has been no rainlately, and the water is low, otherwise we should have fifteen miles ofa ride over the mountain yonder. Keep close to the rocks! Follow me!"
And with this admonition he entered the canon, followed by myself, Gode,and the doctor.