A Description of Active and Extinct Volcanos ... Being the substance of some lectures delivered before the University of Oxford, with much additional matter

Front matter

A DESCRIPTION or ACTIVE AND EXTINCT VOLCANOS. In the present state of geological science, a mineralogist could hardly employ himself hetter, than in traversing those ambiguous countries where so much has been ascribed to the ancient operation of volcanic fire, and marking out what belongs clearly to the erupted or unerupted lavas, and what parts are of doubtful formation, containing no mark by which they may be referred to the one of these, more than to the other. Such a work would contribute very materially to illustrate the Natural History of the Earth. — Illustrations of Hutton' s Theory. A DESCRIPTION OF ACTIVE AND EXTINCT VOLCANOS, OF EARTHQUAKES, AND OF THERMAL SPRINGS; WITH REMARKS ON THE CAUSES OF THESE PHÆNOMENA, THE CHARACTER OF THEIR RESPECTIVE PRODUCTS, AND THEIR INFLUENCE ON THE PAST AND PRESENT CONDITION OF THE GLOBE.

By CHARLES DAUBENY, M.D., F.R.S., FELLOW OF THE GEOLOGICAL AND LINNÆAN SOCIETIES J HONORARY MEMBER OF THE ROYAL IRISH ACADEMY, AND OF THE ROYAL AGRICULTURAL SOCIETY OF ENGLAND J OF THE SOCIETIES OF QUEBEC, MONTREAL, PHILADELPHIA, AND BOSTONJ OF THE ACADEMY OF GENEVA J CORRESPONDING ASSOCIATE OF THE GIOENEAN SOCIETY OF NATURAL HISTORY AT CATANIA, ETC; PROFESSOR OF CHEMISTRY AND OF BOTANY IN THE UNIVERSITY OF OXFORD. TloWa S' tvep8' iidcos nifia Kaierai. SECOND EDITION, GREATLY ENLARGED. LONDON-. RICHARD AND JOHN E. TAYLOR, RED LION COURT, FLEET STREET. 1S4S. PRINTED BY RICHARD AND JOHN E. TAYLOR, RED LION COURT, FLEET STREET. TO JOHN KIDD, M.D., F.R.S., REGIUS PROFESSOR OF MEDICINE AT OXFORD, AND TO The Very Rev. WILLIAM BUCKLAND, D.D., F.R.S., DEAN OF WESTMINSTER, PROFESSOR OF GEOLOGY AND MINERALOGY AT OXFORD, ETC.

ETC. My dear Friends, The lapse of twenty years has only served to strengthen in my mind those sentiments which induced me to dedicate to you, conjointly, the former Edition of this Work. Regarding , which I have never ceased, to do, Chemistry as the Grammar of all those Natural Sciences with which I can pretend to an acquaintance, it is no less my desire now than heretofore to express the gratitude I feel to the Individual who teas my first Instructor in that fascinating Study; and unimportant as may have been the Fruits culled by myself during occasional and somewhat desultory in cursions into the regions of Geology, I ought not to leave out of the account the benefit I have each time derived, after several months of sedentary occupation, from change of scene and a more active mode of life, in estimating VI what I owe to a Pursuit, which holds out the strongest inducements to both.

Preface

TO THE FIRST EDITION. The circumstance of a work like the present proceeding from a Professor of Chemistry seems to call for some explanation ; for notwithstanding the near connexion that subsists between the latter Science and every Department of Geological in quiry, yet it must be confessed, that the Study of Volcanos embraces in itself a field of such extent, that it ought to be entered upon as a principal, rather than as a subordinate occupation. It is fair therefore to myself to mention, that the subject was first taken up at a time when there appeared a reasonable prospect of my obtaining an appointment, which would have entailed the necessity of a five years' absence from my native country. The appointment in question I indeed ultimately lost, owing, as it was understood, to certain doubts that had been started with regard to my eligibility as a Candidate ; but, as I had already formed the plan, and in some degree advanced in the details of the inquiry, I continued to prosecute it at intervals, not only for several years after my hopes of the situation alluded to had been frustrated, but even at a time when the office I afterwards obtained in the University of Oxford might have rendered a somewhat different line of pursuits more appropriate.

PREFACE.

. I have been obliged however in consequence to curtail in a considerable degree the scheme I had formed, which com prehended originally an examination of the Volcanos in the New, as well as of those in the Old World ; and am under the necessity of now bringing forwards as a compilation, many parts of the work in which I had intended to introduce nothing but original matter. It is satisfactory for me however to reflect, that I have visited most of the principal localities in Europe, noticed in my first two Lectures* as the seats of volcanic action, so that with respect to them, even where facts are stated which did not fall within the compass of my own observation, I have been able to ascertain, by going over the same ground, what degree of credit is due to the individuals on whose authority they are given.

In treating of the other Quarters of the Globe in which Volcanos occur, I have spared no pains in availing myself, to the best of my ability, of those resources, which a proximity to extensive public libraries has placed at my disposal, and therefore hope that this part of the work at least may be of use to future travellers ; not merely by putting before them what is already ascertained, but likewise by directing their attention to those points which still require investigation. I venture therefore to offer these Lectures as supplying in some degree, even in their imperfect state, a deficiency long felt in the geological literature of Great Britain • no treatise on the subject of Volcanos having appeared in this language since that of the Abbe Ordinaire, except indeed the recent publication of Mr. Poulett Scrope, which, though containing many ingenious views on the theoretical parts of the subject, is not calculated to supersede the demand for another work, expressly designed to convey a detailed statement of facts, * Comprising what now occupies the first 300 pages of the Work.

PREFACE.

. IX with regard to the characters and situation of the rocks which owe their origin to subterraneous fire. I have only further to add, that the remarks, made at the commencement of the First Lecture, with respect to the little attention that has been paid in Great Britain to the Depart ment of Geology which forms the subject of this work, must be understood as applying solely to that portion of it which relates to Products confessedly Volcanic ; for in no country have more important lights been thrown on the nature of Trap and Basaltic Districts, than by the labours of Dr. Macculloch and of other English Geologists * ; to some of whom I feel personally indebted, either for much of the information which forms the groundwork of such an inquiry, or for the friendly assistance afforded me in the prosecution of it. * See particularly the Memoir on the Coast of Antrim, by my friends the Rev. W. Buckland and W. Conybeare, in th° 'iird volume of the Geo logical Transactions, supplementary to Dr. Berger's paper on the same district.

PREFACE.

TO THE SECOND EDITION. If any apology be thought requisite for reviving at the pre sent time a Treatise that has for many years past been out of print, the mere reference to its present as compared with its original bulk may, it is conceived, suggest reasons that will appear satisfactory. That this increase in its size has not arisen from a more diffuse or discursive mode of writing, will be manifest from a very cursory examination of its contents ; indeed, it may be perceived, that the facts are presented in a more condensed form than heretofore; that much of what appeared less rele vant to the subject has been curtailed or omitted ; and that every effort has been made by the Printer to economise space, by bringing the lines into closer juxtaposition, and by the substitution of a smaller type for the less important portion of the details.

Such, nevertheless, have been the accessions to the mass of our information on the subjects discussed in this Volume which the last twenty years have produced, that whereas in the former Edition the Descriptive Portion occupied only 352 loosely printed pages, in the present it has swollen to no less than 503 ; and that the General Remarks on Volcanic Phænomena, which were heretofore comprised within 80 pages, have now extended themselves to 110.

PREFACE.

. XI Moreover, a still further increase to the size of the volume has been occasioned by my regarding, as Departments of Vol canic Geology, Earthquakes and Thermal Springs, phænomena passed over in a very cursory manner in the former Edition, but occupying nearly 100 pages in the present. In this extension of my design it would have been mani festly absurd to have retained the division into Lectures, in which form the original draft or outline of my Work was moulded : but it will be seen that the same arrangement of the materials is still persevered in, as being, it is conceived, convenient, both in enabling the Reader to grapple with the facts, before his mind is biassed with the hypotheses, and also in rendering the Volume capable of serving as a kind of Guide-book to the Explorers of Districts in which Volcanic phænomena occur abroad, no less than as a Storehouse of Facts for those who reason upon them at home.

In short, if in the imperfect and immature form in which it originally appeared — before the researches of Darwin, of Abich, of Elie de Beaumont, and of a "whole host of other Geological travellers, had shed so much light upon the phæ nomena of Volcanos — my Work met with a favourable recep tion*, as well as a ready sale, it may be offered to the Public with some degree of confidence now, when the subject itself comes invested with a new interest, owing to the connexion between the present phænomena of Volcanos and the past as well as future Revolutions of our Planet, that has been sub stantiated through the important contributions which the persons above-mentioned and so many other of their fellow labourers have rendered to Science. By thus drawing largely from the Investigations of others, as well as from the Memoirs on Volcanic Geology which I have * See especially the Edinburgh Review for March 1827.

PREFACE.

. myself communicated to various Societies since the first pub lication of this Treatise, it has been my endeavour to incorpo rate with the original materials whatever had been added of any value to our stock of knowledge on this subject during the years that have since elapsed ; and although I have not seen reason to abandon the views with which I started, either with respect to the probable cause of volcanic action, or the mode of its operation, my readers, it is conceived, will find the means of correcting my errors on these points placed within their reach, by the faithful report of the phænomena themselves which is presented to their consideration. In a word, whilst avoiding, as much as possible, to chal lenge controversy, I have been far from keeping out of sight, and have rather aimed at giving a prominence to, such state ments and expositions of facts as seemed least in accordance with the Geological opinions now in vogue, thus labouring, so far as in me lies, to correct that one-sidedness of mental vision which is apt to be engendered, by contemplating exclusively one class of geological agents, and by regarding the truths of Science under certain particular aspects.

Above all, it has been my wish to attach to Chemical con siderations their just and proper weight, confident that if I can succeed in so doing, I shall be rewarded by the satisfac tion of having enlisted in the cause of Geology a potent and too much neglected Ally, even though it should, as is very possible, supply weapons to others for the demolition of the theories that I have myself aimed at constructing by its aid. Nov. 30, 1847. CONTENTS.

Chapter I

i _ Pase INTRODUCTORY REMARKS 1

Chapter II. General Nature Of Volcanic Action

General nature of Volcanic action. — Volcanos, how distinguished from other phænomena presenting some ofthe same external appearances. — Characteristics of Volcanic action. — 1. Lava Streams and Ejections of Cellular materials. — 2. Form and Structure of the Mountains in which they appear. — 3. Mechanical and Chemical condition of the individual Rocks. — Glassy and Cellular texture. — Chemical constitution considered. — Felspar the result of Igneous causes. — Mode of distinguishing the nature of the component parts in Volcanic products. — Varieties of Felspar considered. — Difference between Granite and Trachyte. — Varieties of Trachyte considered. — Gradual increase of Bases in other volcanic products, giving rise to the several kinds of Lavas and of Trappean Rocks. — Classification of Volcanic products under two great divisions. — Olivine — Leucitic porphyry — Hypersthene rock, &e. noticed 6

Chapter III. On The Volcanos Of France

Central France. — In Auvergne two classes, ancient and modern, distinguished — their characters. — A few of them particularized, viz. Volvic — Puy de Come — Lake Aidat — Puy Pariou — Puy Graveneire. — Antiquity of the most modem of these considered. — Passage in Sidonius Apolhnaris discussed. — Trachytic cones near Clermont — their formation considered. — Ancient volcanic rocks near Clermont — instances of those of an intermediate age. — Lava of Chaluzet — Montaudoux — Gergpvia — Puy Charade — Puy Marman. — Tufaceous knolls near Clermont. — Volcanic rocks of Mont Dor — their general character. — Basaltic and Trachytic formations considered. — Alum- CONTENTS. Page rock of Mont Dor. — Age of the volcanic rocks in that district, and the probable mode in which they have been brought into their present position. — Volcanic rocks of Cantal — its Trachyte — Basalt — Clinkstone — its age and the mode of its formation. — Volcanic rocks near Puy en Velay — their antiquity — those in the Haut Vivarais ancient — in the Bas Vivarais modem. — Instances of modern Lavas — Aizat — Montpezat — question as to their eruptions having occurred within the historical period. — Volcanic rocks in the south of France — that of Beauheu near Aix. — St. Loup near Agde i 22

Chapter IV. On The Volcanos Of Germany

Volcanos of Germany. — Modern ones in the Eifel. — General characters — distinguished into those of the Upper and Lower Eifel. — Upper Eifel — Gerolstein — Mosenberg — Bertrich. — Lower Eifel — Lake of Laach — Lava of Niedermennig — Basin of Rieden and others. — Trass of Briihl — its origin considered. — Crater of Rodderburg. — Antiquity ofthe Eifel volcanos discussed. Ancient volcanos — near the Rhine — Siebengebirge. — Quarries of Obercassel — Vogelsgebirge — Westerwald. — Basaltic knolls near Eisenach — Pflasterkaute — Budingen — Blaue Kuppe — Meisner — Habichtswald — Steinheim — Odenwald — Black Forest — near Freyburg — near the Lake of Constance — Wirtemburg — Rhongebirge — Fichtelgebirge— Kammerberg near Egra — Toeplitz — Erzgebirge — Riesengebirge — Moravia — near Hof, near Banow. — General remarks on the Volcanic Rocks of Germany 70

Chapter V. Volcanic Rocks Of Hungary

Volcanic rocks of Hungary. — General description of the country. — Five varieties of the Trachytic formation found in it — 1. Trachyte, properly so called — 2. Trachytic Porphyry — 3. Pearlstone — 4. Millstone Trachyte — 5. Pumiceous Conglomerate — re-united — rendered aluminous. — Theory of the formation of Alum. — Other minerals found in the Trachyte. — Synopsis of the Genus Trachyte. — Analogous formations in other countries and in Hungary itself, such as Felspar Porphyry. — Basaltic rocks in Hungary 11/

Chapter VI. Volcanic Rocks Of Transylvania

Direction and extent of the chain.— Trachytic conglomerates and trachytic cones.— Craters near Tuschnad. — Sulphureous vapours at Budoshegy.— Hot springs at Borsah.— Pumice ejected.— Cone of trachyte in Schlavonia. — Cellular basalt near Guns CONTENTS. XV

Chapter VII. Volcanic Rocks Of Styria

Page Volcanos of Styria. — Trachyte of Gleichenberg near Gratz. — Age of the beds surrounding it. — Mode of accounting for the position occupied by the trachyte. — Trachyte of Cilli 136

Chapter VIII. Volcanic Rocks Of Northern Italy

Volcanos of Northern Italy. — Euganean hills. — Trachyte — associated with Scagba. — Vicentin, cellular and compact volcanic rocks. — Monte Bolca. — Bassano. — Formation of the tuff. — Volcanic rocks near Lake Lugano, and Lake Como 139

Chapter IX. Central Italy

Central Italy. — General structure. — Volcanic rocks in Tuscany — Santa Amiata — Radicofani. — Thermal waters of St. Filippo, &c. — Lagunes near Volterra — Acquapendente — Bolseno — Viterbo — Ronciglione — Baccano — Lago di Bracciano — Tolfa. — Neighbourhood of Rome. — Alban hills 151

Chapter X. Southern Italy

General remarks on the volcanos of Southern Italy. — Rocca Monfina — its position described — ancient site of the Aurunci — history of that people — structure of the mountain — nature of the rock which protrudes through the centre of the crater— inferences as to the mode in which the mountain itself must have been formed. Ponza Islands. — Structure of Ponza — Palmarola — Zannone — Ventotienne — San Stefano. — General remarks 174

Chapter XI

volcanos of southern italy (continued) Mount Vultur described — antiquity of its eruptions — peculiar constitution of its lava — configuration of the country when it was in an active state. — Lago di Ansanto — referred to by Virgil — mephitic vapours given out by it — rocks in which they occur — position of the lake with reference to the two volcanos of Vultur and Vesuvius 185

Chapter XII

southern italy (continued). Neighbourhood of Naples — Phlegrean Fields — Tuff or Puzzolana — its height and extent— Grotto of Posilippo — Lake Agnano — Grotto del Cane — Lake Avernus — Monte Barbara — Astroni — other craters contents. XVI Page 195 239 in the tuff.— Trachyte — Piperno— proofs of elevation— Temple of Puzzuoli— Monte Nuovo— Solfatara — action of the gases emitted upon this rock — lava-stream given out from it. Vesuvius — its con dition prior to the Christian æra— first recorded eruption — history of its eruptions up to 1845 — products of its eruptions — its lavas — distinction between those of Somma and Vesuvius. — Monte Somma —how formed— ejected masses— list of minerals, &e. — gaseous pro ducts evolved

Chapter XIII. Islands Of Procida And Ischia

Procida — its structure. — Ischia — its tuff — trachyte — lava-streams — hot springs and vapour issuing from the rocks — eruptions in historical times

Chapter XIV. Lipari Group Of Islands

Stromboli — its crater — unintermitting character of its eruptions — tuff and dykes of lava. Lipari — central portion, consists of tuff — acted on by sulphureous vapours. — Southern portion, composed of pumice and obsidian. — Northern portion the same. — Glassy lavas. Volcano — description of its crater — date of the last eruptions. Panaria described. — Basiluzzo — Salina — Felicudi — Alicudi — Ustica 245

Chapter XV. Volcanic Rocks Of Sicily, Etc

Sulphur beds. — Mud-volcano of Macaluba. — Lago Naftia. — Older volcanic rocks of the Val di Noto. — Mount Etna — description of the volcano — long succession of lava beds and tuts accumulated one above the other — mode in which the mountain was formed — description of its crater. History of its eruptions — antecedent to the Christian æra — subsequent to that epoch. Volcanic energy exerted in the neighbouring parts of the Mediterranean — inferred from the phænomena of the Marobia and sea-quakes experienced ofif the coast — also by the elevation of a new island off the coast of Sciacca. — Products of Mount Etna. Island of Pantellaria — three kinds of igneous formations 264

Chapter XVI. Sardinia

— SPAIN PORTUGAL. Sardinia — modem volcanic rocks— consisting of trachyte — obsidian, &c. Spain— its structure compared with that of Mexico — volcanic rocks — in Catalonia — near Carthagena — Cape de Gaieta. — The Colubretes. Portugal — basaltic rocks near Lisbon. — Indications of volcanos in the Sierra l'Estrella — Cape St. Vincent, &c CONTENTS. XVII

Chapter XVII. Volcanos Of Iceland

Page Other indications of volcanic action on the confines of the Atlantic Ocean in parts appertaining to Europe — L-eland — Scotland — Hebrides — Faroe — Iceland. — The latter island particularly described — its general structure — direction of its active vents — classification of its volcanic products — cavernous lava. — Active volcanos — thennumber and position in the south of the island. — Eruption of 1/85 — 1846. — Volcanos in the north. — Character of the Iceland lavas. — Sulphur mountains. — Geyser springs — their constituents — their high temperature. — Minerals of Iceland. — Surtur brand. Island of Jan Mayen 300 CHiA.PTER XVIII. GRECIAN ARCHIPELAGO. Rhodes and Delos not volcanic. — Nisyros — Santorino and the adjoining islands — accounts of ancient writers — islands thrown up in modern times — how formed according to Von Buch and others — Polycandro — Milo — Argentiere — Poros. — Promontory of Methana— accounts of its upheavement given by the ancients — structure according to modern geologists. — Ægina — Eubœa — Cerigo — Albania — Megalopolis in Arcadia — Mount Parnassus. — Zante, bitumen springs. — Cephalonia, curious phænomenon. — Melida, subterranean noises. — Thermopylæ — Promontory of Mount Athos — Upper Moesia — Servia —Macedonia — Thrace — Bosphorus. — Islands otfthe coast of Thrace — Lemnos — Imbros — Tenedos 316

Chapter XIX. Asia Minor

Volcanic phænomena near the Troas — near Smyrna — Fougues — Ritri — in the interior of Asia Minor — Catacecaumene. — Petrifying springs and Plutonium near the ancient Laodicea. — Traditions with respect to volcanic eruptions in Cilicia — Hassan Dagh — Mount Argæus. — Samos — Patmos — Chimæra in Lycia — Scandaroon 338

Chapter XX. Syria, The Holy Land, And Arabia

Valley of the Jordan volcanic— The Dead Sea— how formed. — Other volcanic appearances in Syria. — Mount Sinai volcanic. — Zibbel Teir. — Aden — near Mecca, &c 350

Chapter XXI. Volcanic

PHÆNOMENA OF PERSIA AND THE ADJOINING COUNTRIES. Circassian range — Mount Ararat — Sapan Dagh — Taman — Baku — Demavend. — Earthquakes in Afghanistan. — Volcanic appearances in Cutch— upheaval and submergence of a tract of land in this province 366 b CONTENTS. XVIII

Chapter XXII. Volcanos Of Central Asia

Page Reports as to volcanos near Khoutche, north of Bokhara— at Mount Tarbagatai— at Mount Tourfan.— Humboldt's opinion.— Erman's doubts as to the existence of real volcanos.— Reports of volcanic phænomena in China 38a

Chapter XXIII. Volcanos Of Kamtschatka And The Chinese Seas

Kamtschatka. — Aleutian Islands. — Kurule Islands. — Japan, viz. in Matsmai — Niphon — Kiu-siu. — Islands adjacent — Loo-Choo — For mosa 391

Chapter XXIV. Indian Archipelago

Philippine Islands : — Lucon — north of Lu^on — south of Luf on — Fuego ■ — Mindanao — Sangir — Siao — Celebes — Gilolo — Morety — Ternate — Tidore — Moth- — Machian — Amboyna — Gounung- Api — Daumer — Timor — Flores — Sumbaya — Java — Sumatra. — Ban-en Island in the Andaman group. — Arracan and Chittagong 399

Chapter XXV. Islands In The Pacific Ocean

Distinction of the islands in the Pacific into low and high. — LOW islands consist of coral reefs — their several kinds described — theory of their formation — by elevation — by subsidence. HIGH islands volcanic. — Sandwich group — Revillagigedo — Galapagos — Island of Juan Fernandez — Society group — Friendly group — New Hebrides — New Caledonia — New Zealand — Chatham Islands — Van Diemen's Land — New Holland — Mount Erebus 415

Chapter XXVI. Islands On The Eastern Coast Of Africa

Madagascar. — Mauritius — basaltic rocks — recent lava-currents. — Isle of Bourbon — extinct volcano of Gros Mome — active volcano — filamentous pumice. — Volcanic rocks to the South of Africa. — Crozet Islands.— Kerguelen's Land.— Islands of St. Peter and St. Paul ... 433

Chapter XXVII. African Continent

Volcanic appearances in Kordoufan— Fezzan and Tripoli Algeria Mount Atlas — Western coast CONTENTS. XIX

Chapter XXVIII. Islands Lying To The West Of Africa

Page Canaries. — Teneriffe, its basaltic rocks, trachytes, lavas. — Palma, its Caldera. — Great Canary — Fortaventura — Lancerote — Madeira — Porto Santo. — Azores — St. Michael — Terceiia — Flores — Giaciosa — Atlantis of the ancients. — Cape Verde Islands — Fuego — St. Jago. — Islands south "of the Equator —Ascension — St. Helena — Fernando Noronha — Tristan d'Acunha 442

Chapter XXIX. West Indian Archipelago

Division of the Islands into four classes : — 1st class — Trinidad, its pitch-lake — Jamaica, extinct volcano — Cuba, upraised beach — St. Domingo — Porto Rico. — 2nd class — Grenada — St. Vincent — St. Lucia — Martinique — Dominica — Guadeloupe — Montserrat — Nevis — St. Christopher's — St. Eustachia. — 3rd class. — 4th class — Antigua 465

Chapter XXX. Volcanos Of North America, Or Above The Isthmus Of Darien

North and Central America — Oregon Territory — California — Mexico — Guatemala 474

Chapter XXXI. Volcanos Of South America, Or South Of The Isthmus Of

DARIEN. General character of the Volcanos of South America — those of Quito — of Peru — Bolivian Andes plutonic — Cordilleras of the coast volcanic — Chili — Patagonia — Tierra del Fuego — South Shetland — ■ General remarks 485

Part II. On

PHÆNOMENA NOT IMMEDIATELY ARISING FROM VOL- CANOS, BUT SUPPOSED TO BE CONNECTED WITH THEM.

Chapter XXXII. On Earthquakes

1st. The Nature of the Earthquake-Shock. — Earthquakes defined. — Three kinds of shock : undulating — succussive — and vorb2 CONTENTS. XX Page ticose— examples of the three kinds. — Instruments for registering earthquake-shocks. — Central earthquakes — linear ones. — Duration of shocks — noises which accompany them — recurrence of shocks — diffusion of shocks through different strata — shocks felt at sea. — 2nd. Dynamics of Earthquakes — Mr. Mallet's views stated... 507

Chapter XXXIII. On Earthquakes

The concomitants, effects, causes, and the physical changes brought about by them. — Flames and gases emitted during earthquakes. — Their influence upon the barometer. Physical changes resulting from them — fissures in the earth — elevations and depressions of the land occasioned. Connexion between earthquakes and volcanos — shown in the case of that of Lisbon — the Caraccas — the West Indies — Scotland. Earthquakes do not arise from electricity — or from the falling-in of caverns. Their probable influence upon the structure of the globe — in elevating and submerging tracts of land, &c 527

Chapter XXXIV. Thermal Springs

— THEIR GEOLOGICAL POSITION Salses or Mud-Volcanos — improperly designated by the latter name — not being amongst the primary effects referable to the action of volcanic forces. Thermal Springs — afford indications of languid volcanic action. — This proved by their immediate connexion with volcanos — active — or extinct — or where not so circumstanced, by being placed at the foot, or in the midst, of some chain of mountains that has been elevated. — Instances of the latter in the Pyrenees — in the Alps. — Where not connected with any great system of mountains, they often proceed from rocks which show evidences of dislocation. — Examples of this, in the thermal springs of Bristol — of Matlock — of Carlsbad — of St. Paul near Carcassone — of Pfeffers — in those of Virginia, &c. 539

Chapter XXXV. Thermal Waters, Their Gaseous Impregnation, Etc

Gases evolved from thermal waters. — Nitrogen — at Bath, its quantity — Buxton, &c. — Cardiff — Clifton — Pyrenees — Sips — Ceylon — United States. Sulphuretted hydrogen. — Carbonic acid.- — Petrifying springs. — Valleys of elevation emitting carbonic acid. — Permanency of physical and chemical properties belonging to thermal waters. — Conclusions deduced from these premises as to the connexion between thermal waters and volcanos. — Tabular view of the properties and temperature of the best-known thermal waters CONTENTS. XXI

Part III. Deductions From The Foregoing Facts

: WITH REFER- ENCE TO THE CAUSES OF VOLCANOS; THE CIRCUM- STANCES THAT INFLUENCE THE CHARACTER OF THEIR PRODUCTS; AND THE USES THEY FULFIL IN THE ECO- NOMY OF NATURE.

Chapter XXXVI. General Statement Of The Various Theories By Means Of Which

THE OPERATIONS OF VOLCANOS HAVE BEEN ACCOUNTED FOR. Page Two classes of theories, chemical and mechanical. Chemical — Lemery's, Breislac's, Davy's — the latter view shown not to be antece dently improbable. The Mechanical theory founded on the internal heat of the globe briefly sketched. — Necessity, in order to decide to which the preference is due, of ascertaining in what degree either one is competent to afford an explanation of the phænomena 593

Chapter XXXVII. General Inferences Respecting The Laws Or Conditions Of Volcanic Action

Local distribution of volcanos — in bnes — and in groups — their general proximity to the sea. — Aeriform fluids evolved. — Bodies not permanently elastic which are evolved as vapours. — Bodies in a solid state ejected — viz. 1st, lavas, their chemical characters — 2ndly, loose fragments thrown out. Relation of these bodies to trachyte — trachyte whence derived. Depth at which volcanic operations proceed. Constitution of a volcanic mountain — mode of its formation. Production of a crater — by eruption — by elevation. — Proofs of the elevation of volcanic mountains — 1st, from their own internal structure — 2ndly, from the existence of domes of trachyte— 3rdly, from the continuous sheets of volcanic matter overspreading large districts — 4thly, from the testimony of eye-witnesses in the case of Santorino — Unalaschka — Graham's Island — Monte Nuovo — Jorullo, &c. Statement of Von Buch's views with regard to craters of eruption and of elevation 603

Chapter Xxxviii. Comparative Estimate Of The Mechanical And Chemical Theories

The two theories equally based upon assumptions. — Mechanical theory explains the protrusion of lava — but does not explain the position of CONTENTS. XXII Page volcanos or other circumstances connected with them — such as the steam and gases evolved — the upheaving force, &c. — Theory modified by supposing water to take part in the operations — gases evolved not explained by this addition — hence combustion of some kind must be inferred— that of the metals of the earths and alkalies affords the most ready solution ofthe phænomena. Objections answered. This view explains the long continuance of the action exerted — mean density of the earth shown to be no objection to it 637

Chapter XXXIX. Statement Of The Chemical Theory Of Volcanos

Primordial condition of the globe nebular — sinking of temperature down to the point at which the denser bodies became liquid — further sinking to the point at which chemical actiou commenced — water and muriatic acid first formed — action of these bodies upon the metals forming the crust of the globe — contraction of the crust from cooling — admission of water to the interiorof the earth a natural consequence of this contraction — formation of volcanic products arising out of this — muriatic acid — sulphuretted hydrogen and other gases evolved — the whole of the hydrogen not emitted from the crater. — Formation of ammonia — of carbonic acid — disengagement of nitrogen explained. — Heat diffused through the crust in consequence of the chemical actions set up. Concluding remarks. — Degree of probability attributed to the different points which the Chemical Theory embraces. — Reasons for putting it forward more prominently than its intrinsic probability may seem to justify 646