1844. 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



39 



THE PHILOSOPHY OF DESERT FORMATIONS. 

 No. 5. 



Were the love of learning to be revived among the Arabians, and 

 did their philosophers turn their particular attention to the modern 

 science of geology, their opinions and theories, suited to the pheno- 

 mena before them, would be peculiar to themselves, and such as era- 

 brace a system of oceanic deposits alone, excluding many of the phe- 

 nomena now so familiar to even the unlearned reader : instead of de- 

 scribing a succession of catastrophes, so strikingly manifest in many of 

 the formations of Europe, their ideas would be confined to the ex- 

 treme simplicity of the desert strata, and to those changes which have 

 taken place in fossil bodies and fossil beds, and by which changes, de- 

 pendent upon climate and position, the mineral kingdom is produced: 

 and could they not avail themselves of modern discoveries, facts 

 which speak for themselves, requiring no interpretation, their ideas 

 would be narrowed to the days of Woodward and others, and their 

 theories would be equally ridiculous. On the other hand, did modern 

 geologists take the trouble of visiting and exploring these lands, sub- 

 mitting with resignation and cheerfulness to the necessary privations 

 and dangers attending these journeyings, there is little doubt but great 

 changes would take place in their respective theories: they would un- 

 doubtedly learn and unlearn much. 



In the preceding chapter I have confined my observations to oceanic 

 fossil formations, and in these are naturally included all desert soils ; 

 but, inasmuch as the mineral kingdom is extensively developed in these 

 wastes, it becomes necessary, in order to explain with perspicuity and 

 simplicity the phenomena of nature, to enter into more minute de- 

 tails of the causes of effects manifest in the creation of rocks, stones, 

 earths, and metalline bodies. The multitude of fossils found in all 

 parts of the earth, arranged in groups and families, forming in many 

 instances entire strata, and generally disseminated over the surface or 

 in the interior beds, attest to the wonderful changes which this plane- 

 tary body has undergone during the revolutions of Time. Exclusive 

 of the magnificent fossil formations of the deserts, which are very 

 often some hundreds of feet in thickness, and which, in fact, compose 

 the entire strata, every portion of the earth exhibits the like phe- 

 nomena of oceanic and mineral formations; the chalk deposits, ex- 

 tending over a great portion of the British isles, northern France, 

 Germany, Denmark, Sweden and Russia, as also in North America, 

 however dissimilar in their lithological composition, agree in their 

 character of oceanic organic bodies; and such may be said of the 

 oolite and shell limestones. On searching into the lower strata, we 

 invariably find fossil bodies analogous to those now forming beneath 

 the waters, or but recently abstracted from them, and so perfect is 

 their state of preservation, that we are enabled not only to identify 

 the genera or order to which they belong, but also to discover the 

 sequence of events and the manifold influences under which they were 

 produced; we distinguish in the Ichthyosauri, ammonites, echini, 

 clumps of coral, and families of shell fish, the once living occupants of 

 quiet seas and tropical heat, which must have lived and propagated 

 their kind in those places where we now find them ; and as Cuvier 

 truly remarks, they are found in elevations far above the level of the 

 ocean, and in places where the sea could not have been conveyed by 

 any existing cause. They are not only included in loose sand, but are 

 often embedded in the hardest stones. Every country, every conti- 

 nent, every island of any size, exhibits the same phenomena. To 

 what other conclusions, therefore, can we come, but that the most 

 elevated parts of the earth were once covered by the waters, that 

 those vast chalk and oolite deposits, hills of carbonate of Hme, and 

 valleys of oceanic marl, owe their origin to oceanic organic bodies ? 

 The varied phenomena also testify, that, although by changes of the 

 earth's axis of rotation, some portions of these elevated lands have 

 been again, and perhaps again submerged, the general appearance of 

 the earth testifies to the operation of very slow causes of effects 

 manifest, as well as to the gradual but universal decrease of the wa- 

 ters. The earths produced by atmospheric influences, although won- 

 derfid to contemplate in their variety and extent, are as nothing com- 

 pared to the oceanic formations, to the existence of which the former 

 owe their origin and many of their peculiar properties ; with the ex- 

 ception of several varieties of schist and basalt, the bulk of aggregate, 

 and in general the entire mass of rocks forming the prominent fea- 

 tures of the earth, are exclusively oceanic, and most of the mineral 

 bodies included in the carboniferous beds are produced by oceanic 

 influences. 



The protean powers of nature are strikingly manifest in the 

 changes which take place from the living body to the mineral com- 

 pound, the same species of shell fish is seen under a variety of forms : 

 it resolves into marl or chalk, it silicifies as flint, it is identified in 



limestone or shell marble, it sometimes consists of several distinct 

 minerals, thus chalk and flint often form separate parts of an echinite, 

 and in Derbyshire, chalk, calcareous spar, bitumen and quartz, are 

 frequently incorporated in the same shell ; many of the after changes 

 are still more beautiful: thus some are converted into Egyptian jasper, 

 others into amethyst quartz, chalcedony, or carnelion. It is only when 

 we follow the order of these changes, and become acquainted with the 

 laws which govern and direct them, that we are enabled to form a 

 correct idea of their extent and importance in nature : thus many of 

 the chalk and oolite formations, and the limestones, have no appearance 

 of organic remains left, in consequence of the gi'neral decomposition 

 of the fossil bodies of which they are composed ; but the material of 

 these bodies is left as an undeniable record of their previous existence, 

 as sure and certain as the comminuted particles of land vegetation, 

 termed earth, denote the previous existence of terrestrial vegetable 

 earth ; and in corroboration of these facts, the same slow but certain 

 changes are continually taking place before our eyes, until they are 

 lost sight of in crystalline bodies. 



Did this earth exist merely by decay and re-production, the pheno- 

 mena of nature would similate to the causes in action, the rocks would 

 moulder into sands and pebbles, and the terrestrial and oceanic matters 

 would be so intimately blended together as to defy classification: but, 

 is such the case ? the oceanic earths, consisting of varieties of sands, 

 marls and Cidcareous matters, limestone rocks, and siliceous bodies, are 

 throughout the by far greater portion of the earth of unmixed quali- 

 ties ; thus vegetable earths are not found in the vast desert beds of 

 the earth, nor does alumina enter into their composition, until such 

 time as they become blended with terrestrial earths, or exposed to 

 long atmospheric action: the syenites, porphyries, busalts, &c., simply 

 siliceous bodies composing these oceanic tracks, are peculiar to them, 

 and peculiar to their respective localities: the carboniferous forma- 

 tions bear an analogy to the formations of Europe and America which 

 have not been intruded upon, by herbaceous plants and other organic 

 products of dry earth : every portion of their soils is the product of 

 organic action, or of action resulting therefrom: every stone is a group 

 of fossil organic bodies, the body or fragment of a body of some in- 

 habitant of the deep : the sands in their primary state principally 

 consist of the comminuted particles of moUusca, but the shelly texture 

 soon disappears after exposure to atmospheric influence : the animal 

 oils have become mineralized, and either preserve their quality as 

 naphtlw,or they enter into combination with other substances, and thus 

 disappear partially or wholly from the view. In all, and through all, 

 we acknowledge the fossil kingdom as the basis of, and the proximate 

 cause of the production of numerous mineral bodies. 



The deserts of Persia are exceedingly extensive, and according to 

 Chaudin, not more than one-tenth part of that country was cultivatible 

 in his time. On the east of the Tigris a considerable desert com- 

 mences, pervaded by the river Ahwaz, and extending to the north of 

 Shuster, about 140 miles in length and 80 in breadth. The great Sa- 

 line desert, including the great desert of Kerman, is about 70U miles 

 long by a medial breadth of 200 miles; attached to this is the desert 

 of Mekran. This immense area, extending 200 miles, is impreg- 

 nated with nitre and other salts, which taint the neighbouring lakes 

 and rivers. The whole country is distinguished for its deficiency of 

 rivers, and a multitude of rocky mountains without vegetation. The 

 soil of the plains is in general stony, sandy, barren, and everywhere so 

 dry, that if it be not watered, it produces nothing, not even grass : 

 even the clays on the banks of the Euphrates are strongly impregnated 

 with muriate of soda. Separated from the great desert of Kerman, 

 and bounded by mountain ranges and the Indian Ocean, are other ex- 

 tensive deserts of Baloochistan. The great desert of Zaharah stretches 

 from the shores of the Atlantic to the confines of Egypt, including a 

 space of 2500 miles in length and 700 in breadth, the whole of which, 

 except a few insulated spots of comparative fertility, are sterile and 

 desolate, consisting of barren plains, shifting sands, and ranges of hills 

 composed of that peculiar class of rocks common to oceanic deposits, 

 and sometimes wholly composed of rock salt. Its borders towards the 

 Atlantic present in many places a succession of sea beaches, the table 

 land rising upwards of 20 feet above the present level of high water. 

 All the great deserts of the earth are most unquestionably ocean beds 

 whence the waters have gradually receded, or otherwise have been 

 suddenly thrown oft' by changes in the earth's plane of position, occa- 

 sioning local or general catastrophe ; where they have gradually re- 

 tired, is evidenced by immense deposits of muriate of soda covering 

 the surface of valleys, and forming hills of considerable magnitude, 

 as well as entire strata disposed beneath the surface: on the other 

 hand, their sudden retiring is denoted by the violence done to the 

 elevated strata, and by the peculiarity of the valleys, which exhibit 

 by strong water lines the rapid retreat of the ocean waters. Most 

 deserts have their peculiarities thus the deserts of Lybia, Syria, 



