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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[March* 



receptacle of this dreadful flood, till becoming swollen above its banks 

 the torrent rollel over the adjacent country sweeping away houses 

 and cattle : the eruption continued for several days longer, accom- 

 panied with terrible roarings of the wind rushing through the craters 

 that had been opened. In May, 1744, the flames forced a passage 

 through several other parts of the sides of the mountain, so that in 

 clear nights, being reflected by the transparent ice, it exhibited a grand 

 illumination. Mud is also ejected from some of the volcanoes of 

 South America, and other portions of the globe, enormous beds of 

 which after long exposure to the atmosphere become solidified as 

 basalt; this is the distinguishing feature of the volcanoes of Java, 

 which rarely emit lava. Vesuvius has also been known to emit 

 torrents of mud ; and, in 1755, Etna vomited forth immense quantities 

 of salt water, with abundance of marine shells. " The volcano in the 

 island of Tanna," says Pallas, "ejects a soft clay, of a bluish ash 

 colour, which seems to be torn from the beds directly over the reser- 

 voir from whence the explosion proceeds : the volcanoes Skaptaa and 

 Skaptaa Seyssel, discharge vast rivers of a muddy consistency, prin- 

 cipally of the nature termed alluvial; and it is said that these streams 

 in 17S3 covered a space of more than ],200 square miles; the lavas 

 of Madeira and the Cape de Verd Islands are little other than mud, 

 the scoriEe, ashes, tufa, &c., being such as to denote the nature of the 

 inner beds from whence they were ejected. The island of Madeira 

 consists of vast beds of commingled terrestrial and oceanic matters, of 

 limestone rising from 2,000 to 3,000 feet above the level of the sea, 

 and abounding with coral and marine shells. Where the internal fire 

 exists among the older formations or mineral beds, the matters ejected 

 are of analogous nature, being metallic scoricE, fragments of crystal- 

 line rocks, &c. The volcanoes of Java, Sumatra, Sulpher Island, in 

 the Loo Choo Archipelago, the Red Sea, Teneriffe, Vesuvius, and 

 nearly all the great volcanoes of the earth, emit vast quantities of 

 sulphur. During one eruption of Etna vast clouds of black sand or 

 powder were ejected, which covered a space of fifteen square miles 

 twelve feet thick. Lava, or streams of melted material, are occa- 

 sionally ejected from the majority of the volcanoes of the earth during 

 eruptions: this material is infinitely diversified in its nature, in con- 

 formity to the beds from whence it was abstracted ; it is sometimes 

 composed of the constituents of vegetable earths or aluminous clays, 

 at other times it consists of lime, lime and magnesia, lime and soda, 

 soda, lime, silica, and iron, in fact, it exhibits every possible variety, 

 and every possible consistence, from a thin watery fluid to a ponderous 

 molten mass, from the simplicity of chalk to the unity of compounds, 

 which distinguish the crystalline rocks ; the lava of no two volcanoes 

 being alike. Even in the lava issued from the same volcanoes 

 there is a marked difl^erence. Thus Von Buch distinguishes on Vesu- 

 vius alone eighteen diflTerent kinds, and the old and new lavas of Etna 

 are readily distinguished by their marked diflTerence from each other. 

 Lava is, in fact, the melted material of the inner beds, the chief con- 

 stituents of which are silex, lime, chloride of sodium, alumine, and 

 potass, which are well known substances belonging to the fossil and 

 mineral kingdoms. Dr. Kennedy's analysis of lava from Etna is given 

 as silica 52, alumine 19, lime lU, oxide of iron 15, soda, the consti- 

 tuents of oceanic soil, unmixed with aluminaries. The permanently 

 elastic fluids given out of volcanoes are muriatic acid, sulphuretted 

 hydrogen, sulphureous acid, aud carbonic acid, the latter being chiefly 

 given out from extinct volcanoes; all these substances are well known 

 constituents of fossil soils, being exceedmgly abundant both in their 

 combined and their uncombined state : petroleum is also given out 

 from some volcanoes in its unchanged state : in the Dead Sea this 

 material is in its natural mineral state, being composed of animal 

 matters, salts, and sulphur. "The sulphur," says Mr. Phillips, "is 

 derived from the mutual decomposition of sulphureous and sulphuret- 

 ted hydrogen, but this material is primarily derived fjom the decom- 

 position of organic matter." Ammonia is evolved in abundance from 

 many volcanoes, being a constituent of animal bodies, and a known 

 constituent of almost all rocks. 



The conditions of preservation of organic bodies are total exclusion 

 from atmospheric and aqueous influence, but no sooner do they be- 

 come exposed to the one or the other than change is the inevitable 

 consequence, and as all change generates heat, so in changing masses 

 the heat must not only in many cases be intense, but extensively ma- 

 nifest. The first effect of the waters upon these fossil beds, in which 

 are combined all the elements of combustion, will be manifest in the 

 earths and alkalis, which greedily abstracting the oxygen and the 

 hydrogen thus set free by the decomposition of the water, will unite 

 ■with the sulphur : again, in the decomposition of bodies thus chemically 

 acted upon, much nitrogen gas is evolved, this being one of the chief 

 constituents of animalized beds; and if muriate of soda be present, 

 which it generally is, muriatic acid gas will also be given oft'; if the 

 nitrogen unites in portions with hydrogen, ammonia is formed, and 



this gas is also evolved from the heated masses, as being one of their 

 primary constituents: hydrogen and sulphur combining, form sulphu- 

 retted hydrogen gas, and if not recombined it evolves through the 

 strata into the atmosphere. 



The surface beds exposed to atmospheric influences soon oxygenize, 

 but the fossils beneath the soil retain their primary conditions, or 

 continue in a changing state, combining and re-combining for indefi- 

 nite periods of time, with no other quantity of oxygen present than 

 belongs to their primary condition, which is always insufficient to 

 effect those permanent alterations necessary to efliect the transition of 

 metalloyds into the state of perfect metals. When we consider the 

 nature of a fossil bed, we can readily conceive the intensity of action 

 consequent on the accidental intrusion of water upon it. It abounds 

 with silica, magnesium, calcium, and sodium, both of which latter 

 alkalis are highly inflammable : sulphur is constantly generating 

 within it, and if muriate of soda, as is the case in censiderable quan- 

 tities, the animal matter is partly converted into bitumen ; under all 

 circumstances it is a wonderful supporter of combustion, and if the 

 carbonate unites with the soda, this compound acts as a flux with 

 silica, and the accidental admission of water kindles the silica, which 

 then burns with great intensity : again, the action of water upon 

 potassium when this alkaline earth is present in the fossil bed, is suf- 

 ficient to support combustion. _ 



Against this theory of generated heat of combustion, it is urged 

 that air as well as water must be present to support combustion, and 

 in order to meet this dithculty. Sir Humphrey Davy was compelled 

 to adopt the vague hypothesis, that the interior of the earth is 

 cavernous, and that these caverns were natural reservoirs for the at- 

 mospheric currents supplied by apertures disposed as the surface of 

 the earth. In all fossil and even in mineral beds vast quantities of 

 azote exist in the latent strata, and when the heat is generated by 

 electro-chemical excitement and increases to the heat of combustion, 

 the electro-chemical disturbance continues to increase with the in- 

 crease of heat. The accident of association, as for instance, the in- 

 troduction of one of the inflammable gases produces atomic excite- 

 ment in the chaotic mass, gaseous evolution of other gases, decompo- 

 sition and re-combination of bodies with bodies, all of which in their 

 expanded volume generate action and re-action accompanied by evo- 

 lution of heat: it is a well-known law of chemistry, that every com- 

 pound elastic fluid, and every consolidated body combines with its 

 molecular particles a certain degree of heat pecular to itself, being 

 capable of receiving an additional quantity of heat, without altera- 

 tion of its physical condition; and, as Dr. Black expresses it, when- 

 ever a body changes its state, it cither combines with caloric or se- 

 parates from caloric; these phenomena are manifest in fossil beds, 

 extensively excited compounds united by slight aftinity are immedi- 

 ately separated, the gaseous products exchange place, disposition, 

 and association, act and re-act upon the several bodies among which 

 they are disposed, or with which they are brought in contact ; and in 

 the general decomposition which ensues the azote of the fixed air is 

 extricated, contributes to assist and maintain silent combustion. We 

 cannot conceive any locality wholly free from fixed air, it is a compo- 

 nent of all the most ponderable rocks, it is disposed in bodies com- 

 posing the earth, and it is one of the chief constituents of animal 

 matter; we have, therefore, good grounds for believing that during the 

 heat of combustion, azote in sufficient quantities is extricated from the 

 strataacted upon to support,maintain,and when other causes are favour- 

 able, to extend that combustion. On the other hand, after eruptions 

 have taken place, and the open crater is formed, a large and continuous 

 supply of air is drawn in by this funnel: communications with the 

 atmosphere is sometimes maintained through the medium of the 

 funnels of extinct volcanoes: air is sometimes communicated through 

 cavernous apertures: it is also communicated with the intruding 

 waters which always hold a certain quantity of air in mechanical 

 combination. 



"All the phenomena," says Professor Phillips, « which are concomi- 

 tant upon volcanic action, seem to admit of explanation, if we will 

 only suppose salt water, and afterwards air, to find admittance into 

 cavities in the interior of the earth, whence they come in contact with 

 the metals, and the earthy or alkaline metalloyds combined with sul- 

 phur there existing." It cannot be denied that chlorine is an abun- 

 dant material of the earth, even in beds the most distant from the sea, 

 and from their elevation most assuredly not subject to the intrusion ot 

 salt water : it is also a well known fact, that all volcanoes are disposed 

 near the sea, and where there are exceptions to this rule, as in Central 

 Asia, they are disposed in the vicinity of the salt lakes, the relics of 

 a former sea, and consequently an oceanic soil: salt beds, and conse- 

 quently saline waters, abound in all quarters of the earth, and most 

 particularly so in fossil soils, where chlorine abounds under numerous 

 forms and combinations, with many bodies having little affinity, and in 



