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THE GEOLOGY 



EXTINCT VOLCANOS 



CENTRAL FRANCE. 



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•* C* ti'tml pas avec il'immenses connoissances qu'on parvient toujours k mieui voir 
que In* nutiw, cVst pur une bonne methode toujours secondee dc robservation. Sur- 
t-iii JVilawnatkifi, < " st ce qui fait que le Chimiste, enferme au milieu de son 
ialCTntuixv et &c *» fnurneaux, est sou vent un mediocre naturaliste et un mauvais 
gfjofagat: tl mH hiuti lit, peut-6tre, comment la Nature a fait dans une pierre; mais 
*:*c«t Jiuui ir» champs, <'est sur la cime des monts, qu'on voit comment elle a fait 
sur h gluW— MnxTUJBiER, £taai «nr to Theorie des Volcans (TAuvergne, p. 139. 

" H u'y * pent-fire jm dans tout runivers une contree ou les terrains volcaniques 
•uiii'tit jiIiih varied niimu lies entre eux, et par consequent plus instructifa, que 
4ms* le milieu ite la France."— Von BUCK, Lettrc a PicteL 




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THE GEOLOGY 



AND 



EXTINCT VOLCANOS 



OF 



CENTRAL FRANCE. 



Bv G. POULETT SCROPE, M.P., F.R.S., F.G.S., &c. 



£eom& ffttition, enbtrgttt gift fmjirobrtr. 



WITH ILLUSTRATIVE MAPS, VIEWS, AND PANORAMIC SKETCHES. 



f>LONDON: 
JOHN MURRAY, ALBEMARLE STREET. 

1858. 



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LOMDON : PRINTKD II V WILLIAM CLOW KB AND SONS, STAMFORD 8TRKKT, 
AMFCUARIMO CROSS. . 



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PREFACE. 



While resident in Italy during the winters of 1817- 
18-19, 1 had observed with great interest the volcanic 
phenomena of Vesuvius, Etna, and the Lipari Isles, 
and paid considerable attention to the structure of the 
district west of the Apennines, between Santa Fiora 
in Tuscany and the Bay of Naples, which presents 
onmistakeable traces of volcanic action on an extensive 
scale, though no eruption has taken place there within 
the historical period. 

After my return to England, being for some time at 
Cambridge, I had the advantage of frequent intercourse 
with the late Professor E. D. Clarke, who was himself 
well acquainted with volcanic Italy, and Professor 
Sedgwick, at that time commencing his distinguished 
career as a geologist. The doctrines of Werner were 
then so completely in the ascendant that it was con- 
sidered little better than heresy to dispute any of 
them. Yet it appeared to me, from the knowledge of 
igneous rocks I had acquired in Italy, that the dogmatic 
canon of that school which denied a volcanic origin 
to the Floetz Trap-rocks (as basalt, clinkstone, and 



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vi PREFACE. 

trachyte were then called), and declared them to be 
precipitations from some archaic ocean, was signally 
erroneous. 

My two friends agreed with me in the opinion that 
the error of the Wernerians in undervaluing, or rather 
despising altogether as of no appreciable value, the 
influence of volcanic forces in the production of the' 
rocks that compose the surface of the globe, formed 
a fatal bar to the progress of sound geological science, 
which it was above all things desirable to remove. 

Being shortly after free to choose my path of travel, 
I determined to examine with care such evidence upon 
this point as might probably be found in Auvergne 
and the neighbouring districts — a country where the 
products of extinct volcanos are brought into contact 
with some of the earliest crystalline rocks, as well as 
with the most recent (tertiary and freshwater) strata. 

For this purpose, in the beginning of June, 1821, I 
established myself at Clermont, the capital of the 
department of the Puy de Dome, and passed some 
months in continual examination of the geology of 
the neighbourhood ; removing from thence, as it became 
convenient, to the Baths of Mont Dore, Le Puy 
(Haute Loire), and Aubenas (Ardeche). I afterwards 
revisited Italy, where I had the good fortune to 
witness by far the most important eruption of Vesuvius 
that has occurred within this century — that of October, 
1822. 



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PREFACE. vii 

On my return to England in 1823, I published a 
volume on the * Phenomena of Volcanos.'* In that 
work unfortunately were included some speculations 
on the9retic cosmogony, which the public mind was 
not at the time prepared to entertain. Nor was this, 
my first attempt at authorship, sufficiently well com- 
posed, arranged, or even printed, to secure a fair 
appreciation for the really sound and, I believe, 
original views on many points of geological interest, 
which it contained. I ought, no doubt, to have begun 
with a description of the striking facts which I was 
prepared to produce from the volcanic regions of 
Central France and Italy, in order to pave the way for 
a favourable reception, or even for a fair hearing, of 
fte theoretic views I had been led from those observa- 
tions to form. 

Indeed this obvious error was pointed out in a very 
friendly manner by the Quarterly Reviewer of this 
Memoir on the ' Geology of Central France,' which 
*as shortly after published.f That article was, I 
believe, the first essay of my distinguished friend 
8ir Charles Lyell, in the path of geological generalisa- 
tion which he has since so successfully pursued. And 
I have sometimes ventured to think that during its 
composition he may have imbibed that philosophical 



* ' Considerations on Volcanos, &c.,' 1825. 
t Quarterly Review for May, 1827. 



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x PREFACE. 

still to appear cascading over the lips of craters of 
scoriae, did assist in no small degree in putting an 
extinguisher on the then fading and flickering, but 
shortly before insolently triumphant, dogma. It had, 
likewise, I may hope, some share in directing attention 
to the vast influence exercised on the crust of the earth, 
not only by volcanic outbursts, but also by the erosive 
forces of rain and rivers, acting slowly and gradually, 
but through periods of immeasurable duration, upon 
the surface of supra-marine land.* 

The edition of this Memoir printed in 1826 soon 
became exhausted. I was, however, unwilling to 
reprint it without previously revisiting the country of 
which the volume treats, and convincing myself of the 
accuracy of its descriptions; but it was only in the 
course of the past summer that I succeeded in accom- 
plishing this. 

Meantime Sir Charles Lyell and Sir Roderick 
Murchison, and many others, had followed me to 
Auvergne, and I had reason to believe were satisfied 
with the fidelity of my views and descriptions. The 
French geologists have also since that time paid 
more attention to this most interesting portion of their 
country than they had previously given to it. And I 
have been gratified to find many of the most trust- 
worthy among them^mt forward views coinciding with 



* See last note. 



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THE GEOLOGY 



EXTINCT VOLCANOS 



CENTRAL FRANCE. 



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xii , PREFACE. 

Doue, ably given in his description of the environs of 
Le Puy. MM. Le Coq and Bonillet have done me 
the honour to take many of my panoramic and other 
views as models for the illustrative engravings to 
their different works on the geology of Auvergne. 
Messrs. Rozet, Pissis, Ruelle, and others, many of 
whom were employed on the Government Geological 
Survey of the country, still in progress under the 
Ecole des Mines, have also printed or communicated to 
the Geological Society of France papers of interest on 
the tertiary and volcanic formations of Central France. 
Great light has likewise been thrown on the Palaeon- 
tology of this district by the zealous researches and 




aptly calls an " inward growth." Observations on the Amount of matter 
composing the dykes, which are so frequent towards the centre of every 
volcanic mountain, would indicate perhaps a proportion of one-sixth or less of 
the substance of the central part of the cone as having been formed in this 
manner. And in some such proportion, elevation, in the sense implied by the 
elevation-crater theorists, may be admitted to have assisted in the production 
of the central summits. But at a distance from these few dykes are found, 
and there is no reason to doubt that the great bulk of such mountains owes 
if i overs caae its formation to the heaping up of ejected matters, whether frag- 
meuLtuy or in the form of congealed lava-currents ; a process which in fact may 
be wl.foemd in active volcanos, as the normal phenomena of every eruption. 
Any other view seems to me opposed not merely to the rules of philosophical 
analogy, but wen to the evidence of the senses. The weight of authority un- 
fortunate! y thrown into the scale in favour of this theory by geologists of such 
reptile utd influence as MM. de Beaumont and Dufresnoy has been the leading 
cause of the uncertain views and imperfect knowledge even now existing among 
French geologists on the great extinct volcanos of their own country. The 
c (I in- to an understanding of a volcanic district must of course be a sound know- 
ledge -I tie " modus operandi" of volcanic action ; and this has been wanting 
in tlif mm idem school of Parisian geologists, with the exception of some few, 
YfUo f like MAI, Provost and Pissis, above mentioned, have had the courage to 
opj>u«t Hn imluence exercised by two or three " great names." 



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PREFACE. xiii 

able publications of MM. Croizet, Jobert, Bravard, 
Aymard, and Pomel. 

The publication of the * Explication de la Carte 
Geologique de la France/ by MM. Elie de Beaumont 
and Dufresnoy, has. not yet reached those chapters in 
which the preface professes an intention to treat of the 
tertiary and volcanic formations of Central France. 
If. Le Coq is, I believe, engaged on a general work 
of this nature on Auvergne, to be illustrated by a 
geological map. But no portion of this work either 
has as yet been made public. 

Under these circumstances, none of the publications, 
whether of French or English writers, which have yet 
appeared can be considered to afford that general view 
or detailed description of the very remarkable series of 
geological facts presented by this country which they 
undoubtedly merit, or which any visitor desirous of 
examining its phenomena would wish to have in his 
hand as a guide. I have therefore been led to suppose 
that a new edition of my Memoir, with such emenda- 
tions and additions as time and the further observations, 
whether of myself or others, might suggest, would be 
acceptable at the present time. It will be seen that 
though I have found it desirable to recast some of the 
introductory chapters, the body of the work is still the 
swfce as was printed in 1826. Indeed on my late visit, 
I found no reason to alter the conclusions I had come to 
in 1821. Not possessing sufficient acquaintance with 



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xiv PREFACE. 

Palaeontology to venture on determining, of my own 
authority, the specific characters of the organic remains 
found in association with the rocks, whether tertiary 
or post-tertiary, of the district, I have given catalogues 
of its fauna from the works of MM. Pomel and Aymard 
in an Appendix, to which the text refers at the proper 
place. The illustrations have been recast and engraved 
on wood on a reduced scale, for the advantage. of 
their being folded into the compass of an 8vo. volume, 
instead of necessitating, as in their original shape, an 
inconvenient accompanying folio atlas. 

Of the maps, that of the Chain of Puys west of Cler- 
mont is nearly in the same state in which it appeared 
in the first edition. And I may add that it was entirely 
compiled from my own observations on the spot, on the 
basis of a sheet of Cassini's old Survey, as I had no 
access at the time to Desmarest's map, from which it 
has, I believe, been supposed that I took the details. 

The other general map of Central France is copied 
from the ' Carte Greologique de France,' of MM. de 
Beaumont and Dufresnoy. 



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CONTENTS. 



CHAPTER I. 

Page 

Sketch or the Geology op Central France 1 



CHAPTER II. 

Tertiary Lacustrine Formations 6* 

1. Limagne d'Auvergne. 2. Cantal. 3. Haute Loire. 4. Montbrison. 

CHAPTER III. 

introductory account of the notices which have been 
hitherto published concerning the volcanic remains ok 
the Interior op France *>. .. 30 

CHAPTER IV. 

General Account op the Volcanic Formations occurring 

upon the elevated Granitic Platform of Central France 37 

CHAPTER V. 

First Volcanic Region. — Monts Dome and the Limauke 

d'Auvergne .. .. 40 

1. Chain of Puys. 2. Products of earlier Eruption**. 

CHAPTER VI. 

R»no!f II. — The Mont Doue 114 

$ 1. The Volcanic Mountain — Its general Outline — Conglomerates. 
§ 2. Structure — Central Peaks — Trachytic Plateaux — Clinkstone 

and Basalt. 
§3. Recent Eruptions. 



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xvi CONTENTS. 



CHAPTER VTI. 



Region III. — Cantal 145 

§ 1. The Volcanic Mountain. § 2, Canton d'Aubrac. 



CHAPTER VI11. 

Region IV. — Departments of the Haute Loire and Abdeche 154 

1 . Mont Mezen : vast Currents of Clinkstone and Basalt- 

Breccias. 

2. More recent Eruptions — Subsequent Excavation of Valleys — 

Human Bones in Volcanic Tuff — Volcanos of the Haut 
Vivarais. 

CHAPTER IX. 

Concluding Remarks 197 

Age of Volcanic Rocks — Gradual Excavation of Valleys — Original 
limits of Lake-basins-'- Probable Changes of Level. 



APPENDIX. 

Catalogues of Oroanic Remains 217 s : 

Table of Heights 232 

■*>ri 
Explanation of the Mai's and Engravings 234 r^ 

-^ 
Imjkx 247 irt./j 

"■ • -* r 



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( xv » ) 



LIST OF ILLUSTRATIONS. 



Piste. 

VI. Valley of Villar and Plateaa of Prudelle To face page 105 

VIII. Clinkstone Rocks, Tuiliere and Sanadoire, from the Puy 

Gros (Mont Dore) „ 136 

X. Montagne de' Bonne vie (a cluster of Basaltic Columns), 

above the Town of Murat (Cantal) „ 150 

XII. Basaltic Plateaux of the Coiron (Arddche), from the 

South „ 163 

XIV. VaUeyofMontpezat(ArdGche) „ 187 

XV. La Coupe d'Ayzac (Arddche) „ 194 

Xm. Profiles and Sections, &c „ 205 

XIII. Volcanic Cone and Basaltic Lava-current of Jaujac 

(Arddche) Frontispiece. 

I. Panoramic View from the Puy Girou, 6 miles South 

of Clermont (Puy de Dfone) At the end of the Volume. 

II. General View of the Chain of Puys, from the West, 

above the Valley of the Sioule, near Pont Gibaud . . „ 

III. Transversal View of the Moots Dome, from the summit 

of the Puy Chopine „ 

IV. Eastern View of Monte Dome, from the Croix de 

Pirobot, between Vol vie and Channat ,» 

V. The Southern Chain of Puys, from the Puyde la Rodde 
VH. Valley of the Dordogne and Mont Dore, from the Puy 

Gros on the North „ 

IX. The Valley of Chambon and the Mont Dore from the East „ 

XI. Panoramic Sketch of the Basin of Le Puy (Haute Loire) 

and of the Mont Mezen, taken from the Mont d'Ours „ 

XVI. Sections of Granitic Plateau from East to West and 
from N.N.E. to S.S.W 

Hip of Central France „ 

Map of Pnys of Auvergne „ 



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I 



GEOLOGY AND EXTINCT VOLCANOS 



CENTRAL FRANCE. 



CHAPTER I, 



GRANITIC PLATEAU AND MARINE 8TRATIFIED FORMATIONS. 

The parallel of 46*30, passing near the towns of Ch&teauroux 
and ChAlons-sur-Sa6ne, will be found to divide France into two 
nearly equal portions, of which the northern may be considered 
as a vast plain, whose waters flow gently towards the north and 
west through the Seine and the lower Lqire. South of this line 
die surface continues to rise with a gradual slope, so as to form 
an inclined plane, whi^h progressively acquires an elevation of 
more than 3000 feet above the sea in the Auvergne and Forez, 
and a still greater in the Gevaudan and Vivarais, where it 
I ; reaches the height of 5500 feet. Here it is abruptly cut down 
by the deep valley of the Rhone, which, running nearly due 
north and south, separates it from the ranges east of that river, 
in the departments Dr6me, Isfere, and Hautes Alpes. On the 
south-west also this high ground rapidly descends through 
broken and irregular embranchments to the basin of the 
Gironde. It may, in fart, be considered as a triangular 



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2 GEOLOGY OF CENTRAL FRANCE. Chap. I. 

platform, tilted up at its south-eastern angle, and declining 
gradually to the north-west. The principal mass of this ele- 
vated district is composed of primary crystalline rocks, chiefly 
granite, overlapped on all sides by secondary strata belonging 
principally to the Jurassic system, which, at its southern 
extremity, attain a considerable elevation in the chain of the 
Cevennes. Abstraction is in this description made of the 
volcanic products which rise, like enormous protuberances, 
from the higher parts of the elevated granitic platform. It 
is also deeply indented by the valleys of the upper Loire and 
Allier. These, on some points, acquire considerable width ; the 
first in the basins of Montbrison and Roanne, the latter in die 
plain of the Limagne. Several detached basins of carboni- 
ferous sandstone occur within this district, seeming to have 
been deposited in hollows or estuaries of the original island 
of primary rocks. And there are vestiges of four geographic- 
ally distinct deposits of as many freshwater lakes belonging to 
the tertiary period, occurring severally in Auvergne, the Forez, 
the Cantal, and the Velay. 

The granite of this district varies much in character, often 
within very narrow limits passing into gneiss, and sometimes, 
especially on its southern and western borders, into mica-schist* 
talcose-schist, or serpentine. The mica 4 is sometimes replaced 
by pinite, either in amorphous nodules or crystallized in hexa- 
gonal prisms. It is here and there traversed by veins and 
dykes of fine-grained granite, of compact felspar, and of felspar 
porphyry. The felspar of the granitic rocks sometimes takes 
the form of large twin crystals, occasionally rose-coloured, like 
those of Baveno. The quartz often also presents beautiful crys- 
tallizations. The amethysts of Le Vernets, near Issoire, have 
long been known in commerce. In metals this primary district 
is not rich. Iron is very generally disseminated, but is only 



* 



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Chap. I. GRANITIC PLATEAU. , 3 

worked on a large scale at Alais (Gard), and at Kive de Gier, 
in the coal-basin of St Etienne (Loire). Near Font Gibaud 
argentiferous sulphuret of lead occurs, and has been wrought 
lately at a considerable expense, but, it is believed, with no 
great success. The same ore occurs near Villefort (Ard&che), 
and in the departments Aveyron and Lot, generally accompanied 
with manganese. The granite round Ardes (Puy de Dome) and 
Massiac (Cantal), and the mica-schist of the Lozfere, are rich in 
antimony. Copper is rare, but some veins in the Aveyron are 
supposed to have been anciently worked by the English when 
they were in possession of the country. Near Limoges and 
St Yrieix the gneiss rock is decomposed into a kaolin of great 
purity, which has long supplied the china factories of Sfevres and 
Paris, and is even exported to the United States. Generally, 
the granite decomposes readily on the exposed surfaces, and pre- 
sents therefore rounded outlines ; while the gneiss, containing 
more quartz and mica, and having a schistose divisionary struc- 
ture, exhibits peaked eminences and precipitous escarpments. 

The mica-schist passes on some points into clay-slate, as near 
Alassac (Correze). With the only other exception of the very 
limited district of Tarare, between the Rhone and Loire, where 
a quartziferous sandstone, probably Devonian, and accompanied 
with anthracite, has been penetrated by a large outburst of 
red porphyry, the entire region of Central Prance contains, I 
believe, scarcely any sedimentary strata more ancient than the 
carboniferous; the Cambrian, Silurian, and Devonian series 
being generally absent The coal-measures are sometimes asso- 
ciated with triassic strata, but much more usually with lias, 
and other members of the Jurassic system. In connection 
with these strata, both arenaceous and calcareous, coal is found 
in detached patches nearly all round the granitic platform, 
and, as already observed, on many points within its limits, 
• b 2 



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4 GEOLOGY OF CENTRAL FRANCE. Chap. I. 

especially' on one straight line erasing it from north-north-east 
to south-south-west, from near Moulins to Mauriac The direc- 
tion of this line is remarkably coincident with the apparent axis 
of the granitic dome, and with the neighbouring volcanic range. 
The most important of these coalfields are at Anton (Saone et 
Iioire) ; Decize (Ni&vre) ; Vfllefranche and Bert (Allier) ; Bras- 
sac, in the basin of the Allier, near Lempde ; St Etienne and 
Rive de Gier (Loire) ; Lavoulte, Frades, and Joyense (Aixl&che) ; 
Alais and Garges (Gard); Crenae and Bedarrieux (H£rault); 
Sansac, Layssac, and Aubin ( Aveyron) ; Brives (Correze) ; Bourg- 
lastic and Bassignac, in the basin of the Dordogne ; Bort and 
St Eloy (Pay de D6me). 

An extensive series of limestone strata, belonging to the lias 
and oolite group, embraces (as has been before observed) the 
whole granitic platform like a frame; on its southern border 
especially, these calcareous rocks assume a remarkable develop- 
ment, forming a large proportion of the surface of the depart- 
ments Aveyron, Lozere, Gard, and Aitfeche. They constitute a 
vast elevated platform, sloping gradually from the primary range 
towards the south-west, and intersected by a few deep gorges, 
scarcely wider anywhere than the bed of the river that flows at 
the bottom of each. The stratification' being nearly horizontal, 
though dipping to the south or south-west this formation exhibits 
a series of flat-topped hills bounded by perpendicular cliffs 600 
or 800 feet high. These plateaux are called " causses" in the 
provincial dialect, and they have a singularly dreary and desert 
aspect from the monotony of their form and their barren and 
rocky character. The valleys which separate them are rarely of 
considerable width; winding, narrow, and all but impasBable 
cleft-like glens predominate, giving to the "Cevennes" that 
peculiarly intricate character which enabled its Protestant 
inhabitants in the beginning of the last century to offer so 



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Chap. I. SECONDARY FORMATIONS. 5 

stubborn and gallant a resistance to the atrocious persecutions 
of Louis XIV. 

The lias underlying the oolitic beds is often represented by 
blue schistose marls or sandstone, and occasionally by magnesian 
limestone, especially in the departments of Dordogne, Lot, and 
Aveyron. 



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Chap. II. UMAGNE D'AUVERGNE. T 

I. Lacustrine Formation op the Limagne d'Auvergne. 

The largest of these lakes covered the surface now occupied 
by the wide and fertile valley of the Allier, called la Limagne 
d'Auvergne, extending from Brioude in the south to some 
distance beyond Moulins on the north, having an average width 
of near twenty miles. It was bounded laterally by two parallel 
granitic ranges, that of the Forez, which divides the waters of 
the Loire and Allier on the east, and that of the Monte Domes, 
which separates the Allier from the Sioule on the west An arm 
of the same lake also evidently reached some way up the valley 
of the Loire from the junction of that river and the Allier to the 
neighbourhood of Boanne. The lower levels of this great valley- 
plain are for the most part superficially covered with alluvium, 
composed chiefly of pebbles of granite, gneiss, trachyte, and 
basalt* The substratum, wherever it shows itself, consists of 
nearly horizontal strata of sand, sandstone, calcareous marl, clay, 
or limestone, none of which observe a fixed and invariable order 
of superposition. Several hills also composed of the same strata 
rise from the plain, generally connected more or less with the 
granite ranges on either side. They were very justly described 
by M. Kamond, writing in 181 5,t as " scattered relics of a series 
of beds which once covered the actual surface of the valley, 
and constituted an ancient plain much above the level of the 
present one." 

Many of these fragments have evidently been protected from 
the destruction that has involved* the greater part of the forma- 
tion by a covering of basalt ; others owe their preservation to a 

* The compilers of the ' Carte Geo- pebbles of basalt, and generally occur- 

legtque de la France' class these alia- ring at higher levels, than the existing 

vial beds into two divisions, one sup- river-beds. But these distinctions do 

posed to be of recent origin, the other not seem to me as yet well made out. 
referred to the Pliocene or upper Ter- f Me*moire but le Nivellement des 

tiary period, from its containing fewer Monte Domes. 



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8 LMAGNE D'AUVERGNE : Chap. U. 

similar capping of horizontal strata of a hard and durable lime- 
stone of a stalagmitic character to be described hereafter. These 
hills are .seldom found in immediate union with the granite 
ranges, but are in general separated from them by shallow trans- 
verse valleys, so that the precise junction of the two formations 
is not often observable. But where this can be seen the lowest 
arenaceous beds are usually found to lean against the granite, 
sometimes at a considerable angle. 

The principal divisions of the lacustrine series may be classed 
as — 1st, grit and conglomerate, associated with red, blue, and 
white marls and sandstones; 2ndly, green and white foliated 
marls ; 3rdly, limestone or travertin, often oolitic. 

1. The sandstones and conglomerates forming the first or 
lowest of these divisions were considered by M. Brongniart, who 
gave them the name of " Arkose," to be of secondary and marine 
formation, and to be much anterior to the lacustrine strata with 
which they are associated ; and several of the French geologists 
have followed him in this view. As they rarely contain any 
definite organic remains, either alternative seems at first 
tenable. But on a closer examination there is no difficulty in 
recognising the occasional alternation of these sandstone-beds 
with the calcareous strata containing freshwater shells,* and 
I have therefore no doubt of their belonging to the lacustrine 
series. They usually are seen resting directly on the granite 
edges of the basin, from the detritus of which they are evidently 
derived. Some beds consist of a conglomerate of worn pebbles 
and fragments of granite, gneiss, mica-schist^ porphyry, the 
rocks of the adjoining elevated district, but without the admix- 
ture of basaltic or any other volcanic rocks. These arenaceous 
strata are not continuous round the margin of the lake basin, 
being rather disposed here and there, like the independent deltas 



* For example, in the hill* called lea G6tea and Chanturgue near Clermont. 



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Chap. II. DIVISIONS OF LACUSTRINE SERIES. 9 

which grow at the mouths of torrents, along the borders of 
existing lakes.* 

Other beds consist of a quartzose grit formed of separate 
crystals of quartz, mica, and felspar, evidently formed m eitu 
from the disintegrated materials of the granite on which they 
rest, and from which they are scarcely to be distinguished The 
cement is generally siliceous, and the resulting rock is some- 
times hard enough to be used for millstones. At other times 
the cementing matter is calcareous, and the stone more brittle. 
The calcareous matter sometimes is aggregated into nodular 
concretions, passing into solid beds of limestone resembling the 
Italian travertin or the deposits of mineral springs. It occa- 
sionally contains crystallized sulphate of barytes in veins, chal- 
cedony, and bitumen. The most largely developed of these 
arenaceous beds are, however, those of red, blue, and yellow 
marls and sandstones, which present an aspect absolutely iden- 
tical with the secondary new red sandstone and marl of England. 
Some of these gtrata are very friable, others sufficiently compact 
to be quarried for building-stone* They are, like the con- 
glomerates above mentioned, with which they occasionally* 
alternate, evidently derived for the most part from the degrada- 
tion of the adjoining granite or gneiss, which is in fact seen to 
decompose into an alluvium very similar to these tertiary sands 
and marls. The calcateous element, where it occurs, was, no 
doubt, added from the interior of the primary crystalline rocks, 
whence even now issue many springs depositing large quantities 
of carbonate of lime, and which must have been the source of 
the far greater bulk of that material composing the marly strata 
generally superimposed to the sandstones. 

2. Green and white foliated marls. Sir Charles Lyell observes 



Lyell, Man., p. 698. 



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IMAfiSX irArVTBOOB : Our. IL 




of 
grits and coo- 
ky the redaction of the 
■L tad the decomposition 

of Mm from the apings, 
woaid uitai iDy be carried 
Ike share than die coarser 
■i the nunediate neighbour* 
chalky maris certainly 
of 600 or 700 feet They are 
for the WKt part cither light veUowisi green or white, and 
have Terr much die aspect of chalk, with, like it, a semicoo- 
choadal fracture when die strata are flrfEaentiy thick. Usually, 
however, they are thinly foliated— « character which arises 
from the innumerable thin shells, or carapace valves, of that 
minute animal called cypris, which is known to moult its 
internments periodically, differing in this frojn the conchi- 
feroos moUoska. On other points flattened stems of chane, 
or myriads of small pabdnne or other freshwater shells, may 
be observed by the microscope to occasion this foliation, which 
is carried to such a degree that twenty or thirty laminae may 
often be counted in the thickness of an inch. 

3. Interstratified with the marls we find thick beds of an 
oolitic limestone resembling our Bath stone in colour and struc- 
ture, and, like it, acquiring greater hardness on exposure to the 
air. At Gannat and elsewhere this rock contains land-sheik 
and bones of quadrupeds and birds. At Chadrat the oolitic 
grains are so large as to deserve the name of pisolites, the small 
spheroids combining both the radiated and concentric structure. 
But the most remarkable form assumed by this freshwater 
limestone is that called " Indusial," from the coses, or indusiie, 



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Cmap. EL INDU8IAL LIMESTONE. 11 

of caddis-worms (the larvae of Phrygane®), great heaps of which 
have been incrnsted as they lay by carbonate of lime, and 
farmed into a hard travertin or stalagmitic limestone. This 
rook is seen sometimes to farm ranges of concretionary nodules, 
at others continuous beds, one over another, with layers of the 
foliated marls interposed. 

It is well known that certain varieties of the Phryganea (or 
caddis-fly) are in the habit, when in their caterpillar state, of 
clothing their bodies with a cylindrical case composed entirely 
of minute river-shells of some single species — helices, mytili, 
planorbes, or other — united by glutinous filamems, and disposed 
in some sort of order around. These habitations are quitted 
when the insect's metamorphosis is completed; and on the 
banks of rivers or marshes frequented by them, heaps of such 
empty cases may be observed. If we suppose them in this state 
to be exposed to be incrnsted by calcareous matter from the 
depositions of some neighbouring spring, they will assume pre- 
cisely the appearance of the remarkable rock which we find in 
Auvergne, composing repeated strata of considerable bulk, alter- 
nating through a thickness of several hundred feet with the 
more ordinary marls. The surfaces of these beds are usually 
mammillated or botryoidal, and the calcareous matter enveloping 
the Indusueis arranged concentrically in the manner of a stalag- 
mite. Where the bed is thinnest, the continuity is often inter- 
rupted or prolonged in separate nodular concretions of the same 
kind imbedded in loose sand. The minute shells surrounding 
the larvarcases are usually the Bulimus atomus of Brongniart, or 
a small Paludina. More than a hundred of these shells may be 
counted round a single tube, and ten or twelve tubes may be 
found packed together irregularly in a single cubic inch of the 
rock. When it is added that repeated strata of this kind eight 
or ten feet thick appear to have covered very many square 



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Chap:II. ORGANIC REMAINS. IS 

some resemble in mineral character the secondary lithographic 
limestone of Ch&teauroux. The calcareous marls often contain 
much gypsum, selenite filling the fissures of the rock and of the 
associated marls ; and that so abundantly as to be extracted for 
commercial purposes — as at the Puys de Coran, de Millefleur, 
and the Butte de Montpensier. 

In general it is in the more solid strata just described, rather 
than in the large intervening deposits of white, soft, foliated 
marls, that are found the remains not only of mollusks, but 
also of the vertebrated animals, of which a very copious cata- 
logue has been published by M. Pomel.* Carnivora, Insectivora, 
Rodentes, Ungulata in numbers ; and among them the anthraco- 
therium, rhinoceros, dinotherium, coenotherium, and palaeocherus ; 
Ruminants, crocodiles, tortoises, lacerte, birds, serpents, fish, and 
batrachians are also frequent All these, says M. Pomel, seem 
properly to belong to those great deposits of concretionary 
indusial limestone which form so important an element in the 
geognosy of the whole Limagne.f This is in fact what would be 
expected from the littoral origin we have already ascribed to the 
contents of these beds. M. Fomel declares the result of the exami- 
nation of his catalogue to be that all the ossiferous deposits of the 
Limagne lake belong to the same geological and zoological pe- 
riod (the Lower Miocene), and cannot be divided into periods by 
reason of their palaeontological characters, since the same species 
are found in the oldest as in the most recent beds of this formation. 
Whatever differences occur are such only as are found in the exist- 
ing fauna, and may be referred to differences in geographical or 
climatic situation, in the habits or the greater or less extension 
of species, to accidents of deposition or fossilization. With 



* This catalogue will be found in the Fossiles, decouverts dans le Bassin de 
Appendix. la Loire BupeYieure et de l'AHier. Paris, 

f Pomel, Catalogue des Vertebras 1854, p. 151. 



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14 LIMAGNE D'AUVERGNE: Chap. II. 

respect to the question of correspondence in point of age of the 
lacustrine deposits of the Limagne with other well-known tertiary 
formations, M. Pomel exhibits more doubt, but on the whole 
concludes from pakeontological evidence that they may be con- 
sidered as parallel to the fossiliferous beds of Mayence, more 
recent than the gypsum of the Paris basin, but older than the 
Faluns of Touraine — a classification which corresponds vary 
closely with the opinion of Sir Charles Lyell, who, after hesi- 
tating for some time as to whether these Auvergne deposits 
belonged to the upper members of his Eocene formation, or to 
the lower ones of the Miocene, has, I have reason to believe, 
made up his mind to consider them as of the age of the latter 
division of the tertiary series.* 

These remarks refer, of course, to the lacustrine strata alone of 
the Limagne, not to certain later ossiferous alluvial deposits, such 
as occur at the noted localities of Mont Perrier and Pardines, 
which belong to a period when the volcanos of this country had 
been long in activity, the lake certainly drained, its strata largely 
denuded, and deep and wide valleys channelled out through 
them. To these I shall revert in a later page. 

No traces of rocks of a volcanic character occur in the con- 
glomerates or sandstones which constitute the lower terms of 
this freshwater formation. But higher in the series a mixture 
is here and there to be observed of the products of neighbouring 
volcanic eruptions with the calcareous beds. In occasional in- 
stances fragments of basaltic lava, crystals of augite, scoriae, 
and volcanic ashes are scattered through some of the undis- 
turbed limestone-beds, and assume frequently a remarkable 
disposition, the heavier and larger fj-agments occupying the 
lower part of each stratum, the lighter and smaller stopping in 



• See the Supplement to his fifth edition of the Manual (Murray, 1857). 



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Chap. H. 



CALCARBO-VOLCANIC STRATA. 



15 



the upper parts — suggesting the obvious idea that these fragments, 
after ejection from a volcanic vent, had fallen through the air 
into the lake at the time the stratum in which they occur was 
in the condition of very soft calcareous mud. Geologists will 
probably see in this fact some analogy to the arrangement of 
the layers of flint nodules in common chalk strata.* I have 
observed strata of this character on the mountain of Gergovia 
and several other points; but the most remarkable example 
may be seen on the banks of the Allier immediately above Pont 

a 




L Cliff on the Banks of the Allier, near Font dn Chateau, at the base of the Pay de DalleU 

du Ch&teau. The river here flows at the foot of a line of cliff, 
which it is continually undermining, and thus exposes a regular 
vertical section rather more than 100 feet in height (See 
the woodcut above.) 

The upper surface of the cliff is horizontal, and formed to the 
depth of 8 or 10 feet of a bed of boulders exactly the same as 
those which the river still rolls along its bed below. The strata 
beneath are not completely horizontal, but have a slight curve 
rising upwards at each extremity of the exposed cliff, as if they 
had been deposited in a hollow, or perhaps subjected to some 
amount of disturbance since their deposition. 



* In which case likewise "it seems 
as if there had been time for each suc- 
cessive accumulation of calcareous mud 
to become partially consolidated, and 
for a re-arrangement of its particles to 



take place (the heavier sUex sinking to the 
bottom), before the next stratum was 
superimposed." — LyeWs Manual, 5th ed., 
p. 244. 



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16 LIMAONE D'AUV-ERGNE : Chap. 11. 

1. The lowest visible beds consist of a compact brownish grey 
limestone containing much fragmentary volcanic matter, gene- 
rally arranged as above described in each stratum according to 
their respective gravities, the largest fragments at the bottom, 
the rest diminishing in size in proportion to their distance from 
thence. These beds dip rapidly below the level of the river, 
and are covered by — 

2. A bed about 4 feet thick of a coarse-grained limestone of 
an ochreous yellow colour and earthy fracture, without any 
visible admixture of volcanic matter. It contains the casts of 
numerous shells, Planorbes, Helices, Lymnei, the shells being 
often replaced by bitumen, which exudes likewise from fissures 
in the rock. This is a very common variety of the hard lime- 
stone beds frequent throughout the lacustrine series. 

3. Above this is a considerable thickness of the soft white 
foliated marly limestone, characteristic of the formation, having 
a plain fracture, sometimes slightly conchoidal, strongly adher- 
ing to the tongue, with an earthy smell, its exposed surfaces 
occasionally presenting efflorescent carbonate of soda. It has 
frequently a tendency to desquamate in globular masses. 

4. A single bed, 10 inches thick, of a very compact, hard, and 
fine-grained limestone, with a conchoidal fracture, of a deep 
bluish-black, probably coloured by volcanic ashes.' 

5. Numerous calcareo-volcanic strata, similar to No. 1 ; some 
of them being ribboned with different colours, yellow, brown, or 
bluish-black, determined, it seems, by the greater or less pro- 
portion of volcanic ashes contained in their several zones. 
Where this proportion is considerable the rock generally has the 
more compact character and conchoidal fracture ; and by still 
farther increase of the volcanic element it passes into a kind of 
poporino or basaltic breccia, which often affects a globular con- 
nvtionarv structure. 



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Chap. II. CALCAREO-VOLCANIC. STRATA. 17 

The strata interspersed with volcanic matter are perfectly 
parallel to those that are free from it, and present all the cha- 
racters that we should expect in sediment slowly and tranquilly 
deposited in a body of water into which repeated showers of vol- 
canic ashes and fragments were occasionally ejected from some 
neighbouring volcano in active eruption. Immediately behind 
this cliff rises the Puy de Dallet (6 in woodcut), an isolated 
hill about 900 feet high above the river, composed entirely of 
repeated strata of the freshwater limestone and marls, with the 
exception of a heavy capping of basalt And in the ravines 
with which it is scored, sections are afforded sufficient to make 
it abundantly plain that the beds already described in the cliff 
alongside the Allier pass under the entire hill. 

Some of the strata composing the Puy de Dallet are very 
siliceous, some oolitic, and the upper beds are of the concre- 
tionary indusial variety. The basaltic platform rests imme- 
diately on a thick bed which contains much volcanic matter, and 
is in feet a basaltic breccia, mixed with calcareous particles. 
It is compact, and seems at a distance irregularly columnar, as 
is the superimposed basalt 

Here we have unquestionable proof that volcanic eruptions of 
basaltic lava and scoriae occurred within or on the banks of the 
freshwater lake of the Limagne long before it had ceased to 
deposit sediment ; since a thickness of several hundred feet of 
its sedimentary beds are found overlying some which contain 
numerous fragments of volcanic character. In the mountain of 
Gergovia a similar alternation is to be seen of beds of limestone 
and marls with others containing numerous fragmentary volcanic 
matters, often in such abundance as to compose far the greater 
part of the rock and give it the character of a peperino. This ' 
hill also is capped by an enormous platform of basalt: and 
another thick bed of the same rock crops out from the side of 

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Chap. II. 



CALCAREOUS PEPERINO. 



19 



quantity of fine specimens of radiated arragonite occurs, in veins, 
some of which are a foot in thickness. They intersect the rock 
in such numbers as to give it a reticulated appearance. A range 
of hill consisting solely of the same calcareous peperino is con- 
tinued for about two miles towards the south. 

Above the village of Chauriat it presents a very compact and 
hard stone, composed of small unequal fragments of augitic 
basalt firmly united by a fine cement of calc spar. It is diffi- 
cult, while examining this rock, to believe that the basaltic 
parts are in reality mere fragments, and the impression is 
strongly excited that its peculiar structure is owing to a separa- 
tion of dissimilar substances during the consolidation of a lava 
which by some mechanical cause had been universally penetrated 
with calcareous matter.* 

La Montagrie de Cour-cour, an insulated hill of considerable 
size rising alone from the plain near Beauregard, is of the same 
nature. The peperino hertf is traversed by irregular venous 
masses of dark-grey basalt Arragonite is not so abundant as at 
Verthaison. 



* The calcareous peperino of the 
Vicentin (Montecchio Maggiore) ex- 
hibits some very similar mixtures of 
basalt and calcareous spar, which it is 
difficult to refer decidedly either to the 
conglomerate or the solid lava-rock. 

In giving the name of peperino to a 
volcanic conglomerate consisting of 
fragments of basalt and scoria, without 
pamioe or any trachytic matter, united 
either by simple adhesion or a calcareous 
or argillaceous cement, I follow the 
Italian geologists, who have continued 
this trivial term to a similar rock, which 
also, like that under consideration, oc- 
casionally contains fragments of lime- 
stoae and primitive rocks, bituminized 
wood, &c. Ac. — Vide Broochi, Catalogo 
ragionato di Roooe, pp. 45, 47. 

There exists the strongest analogy 



between the calcareous peperino of the 
Limagne and that of the Vicentin, the 
latter being without doubt the result of 
volcanic eruptions breaking forth from 
the bottom of the sea, in which vast 
masses of calcareous matter (of the Plio- 
cene tertiary formation) lay in a pulpy 
unconsolidated state; the former of 
eruptions through a similar mass, the 
deposit of & freshwater lake. The great 
variety of rare and beautiful crystalliza- 
tions to which this violent mixture of 
calcareous matter with incandescent 
lava has given rise in both localities, is 
remarkable. .Mesotype, stilbite, arra- 
gonite, chalcedony, and numerous forms 
of calcareous spar, abound in the drusy 
and vesicular cavities and veins of both 
these conglomerates. 

c 2 



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Chap. II. CALCARIFEBOUS SPRINGS. 21 

The rock upon which stands part of the town is traversed by 
fissures from which a prodigious abundance of viscid bitumen 
exudes spontaneously. The cheeks of these clefts are frequently 
lined with mammillae of chalcedony, and from these occasionally 
spring the most graceful groups of small rock-crystals diverging 
from a central point, and spread out with the regularity of the 
petals of a marigold The union within a single specimen of the 
smallest dimensions, of volcanic scoriae, limestone, chalcedony, 
rock-crystal, and bitumen, is singular. 

Some of the upper parts of this rock present a spheroidal 
structure, similar to what often occurs in basalt The spheroids 
are from two feet to a few inches in diameter. They exfoliate 
by decomposition in concentric coats like those of an onion. 
This configuration appears remarkable in a conglomerate, but 
is not unusual in the " wackes " (as they have been generally 
called) which accompany the older basalts. Veins of compact 
fine-grained and siliceous limestone, free from visible basaltic 
particles* though of a light-brown colour, pierce through this 
rock occasionally from below, and mix intimately with it at the 
line of contact 

The Puys de la Poix and de Crouel, and the low hill on which 
Clermont stands,* consist of a similar species of peperino, bearing 
equally the appearance of a violent and intimate union of 
volcanic fragmentary matter with limestone while yet in a soft 
state. They enclose ill-defined masses and veins of pure lime- 
stone, some bituminized wood, chalcedony, and bitumen. The 
latter substance formerly exuded in great abundance from the 
Puy de la Poix, but the source at present seems exhausted 

At the northern base of the hill upon which Clermont is built 
rises a spring, the water of which is impregnated by means of 



* Noa. 9<), 89, and 88, in our map of the Monte Domes. 



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22 



LDIAONE ITAUVKRONE: 



Chap. IL 



its carbonic acid with so large a proportion of carbonate of lime, 
which it deposits on issuing into the air, that its incrustations 
have formed an elevated natural aqueduct 240 feet in length, 
and terminating in an arch thrown across the stream it originally 







2. Natural Bridgt M Travertin, formed by an tocrmtfng Spring at Clermont 

flowed into, 16 feet high and 12 wide. Near it are the rudi- 
ments of a similar arch, the construction of which is still going 
on, and aptly illustrate the formation of the other. Like many 
other similar incrusting springs in different countries, it has 
been turned into a source of emolument by the proprietor, who 
breaks the fall of the water in such a manner that its stony 
particles may be deposited on various natural objects exposed 
to its spray. At the time of my visit the stuffed skins of 
a horse and a cow were undergoing this petrifying process, as 
well as the usual projwrtion of birds, fruit, flowers, medals, 
cameos, &c. 



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Chap. II. CALCARIFEROUS SPRINGS. 23 

There are several other springs in Auvergne possessed in a 
high degree of the same qualities. One at Chalucet, near Pont- 
gibaud ; another, called La Fontaine de Rambon, on the banks 
of the Crouze, near St Floret On both sides of this river, and 
for a considerable distance down the gorge it flows in, are seen 
colossal fragments of calcareous travertin, which by their position 
prove this mineral spring to have once erected a bridge similar 
to that of St Alyre at Clermont but exceeding it prodigiously 
in dimensions, and probably choking up the whole valley, since 
the source itself is elevated more than 100 feet above the river. 

It is worthy of remark that the three springs mentioned above, 
whose deposits are, except in a greater or less proportion of iron, 
exactly alike, rise from rocks of different kinds : the first from a 
calcareous peperino; the second, from the foot of a regular 
volcanic cone, at least twenty miles from any calcareous rock ; 
the third, from granite. It is apparent from this that all have 
their origin in or below the granitic rocks which form the basis 
of the whole territory, and which include or cover the volcanic 
focus whence in reality these mineral springs in all probability 
ultimately derive. The same observation applies to the many 
thermal sources which occur on various points of the platform, 
springing indifferently from primitive or volcanic rocks ; as at 
Mont Dore les Bains, La Bourboule, St Nectaire, CMtelguyon, 
Gimeaux, N6ris, Vichy, Vic en Carlad&z, Chaudesaigues, &c. 
Some of these deposit a travertin having much silex as well as 
carbonate of lime in its composition, and arragonite is occasion- 
ally found to have crystallized in its fissures. There appears 
reason to believe that the quantity of mineral matter brought to 
the surface by such springs was much greater in earlier times, 
and is still annually diminishing. 



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Chap. It BASIN OF HAUTE LOIRE. 25 

of chare, preserved in them. Several hills are seen in the 
neighbourhood of Aurillac composed of such strata two or three 
hundred feet in thickness. They are generally covered by 
massive beds of volcanic breccia, trachyte, and basalt. In somfe 
places, as between Aurillac and Folminhac, there appear to be 
a confusion, and occasional alternations, of the volcanic and 
calcareous beds, similar to what has been described in the 
Limagne formation. 

The original limits of the lake-basin of the Cantal can with 
difficulty be ascertained, owing to the colossal proportions of the 
volcanic mountain in the vicinity, by whose products its deposits 
have been overwhelmed. They are found, however, beneath the 
volcanic beds wherever any torrent discloses the inferior strata, 
within a space limited by lines passing through Jussac, Vic en 
Carlad&z, Mur de Barr&z, and Panet But as they reappear on 
the north-east side of the central heights of the Cantal, near 
Murat, bearing the same characters as in the valleys of the Cfere, 
the Goule, and the Jourdanne, it seems probable that the lake 
was continuous through the intervening area. 

HL Basin op the Haute Loire. 
The freshwater formation of the basin of the Upper Loire which 
surrounds Le Puy differs but slightly from the two already 
described, and, like these, has been covered in part by prodigious 
and repeated extravasations of volcanic matter, which have 
loaded its generally-horizontal strata with massive coverings of 
basalt and basaltic breccia three or four hundred feet in thick- 
ness. It is, therefore, in general only by tracing up the deep 
waterworn ravines which furrow these superimposed rocks that 
the extent of the lacustrine deposits can be observed : the main 
valley of the Loire, however, and some of its tributaries, offer an 
ampler view of the beds through which* they have been excavated. 



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Chap. IL BASIN OF HAUTE LOIRE. , 27 

layers of flint passing into semi-opal, especially in the vicinity of 
volcanic rocks. At St Pierre Eynac these siliceous strata 
evidently pass under the powerful clinkstone mass of Montplaux. 
Towards the middle of the basin the clayey marls alternate with 
beds of gypsum, several of which are sufficiently rich to be 
worked for agricultural and other uses. The shells contained in 
these beds are of lacustrine or marshy species ; bones also occur 
in them, and the remains of fish, Crustacea, birds, and their eggs.* 
Above the marls with gypsum is usually a considerable thick- 
ness of calcareous and foliated marly strata, alternating with 
greyish limestone of the consistence of chalk, having tubular 
cavities attesting its palustrine origin, and numerous casts of 
planorbes, limnei, cyclostomae, bulimi, cyprides, &c. Bones and 
teeth of animals, both terrestrial and aquatic, are also found in 
them abundantly, for a catalogue of which I must refer toM.Pomel.t 
In one site alone, the hill of Bonzon, and nearly in one bed, so 
large a number and variety of organic remains occur as almost 
to furnish a complete Fauna of the district at the period of its 
deposition, which MM. Pomel, Aymard, and Lyell unite in 
referring to the Lower Miocene. 

There is no clear evidence of the outburst of any neighbouring 
volcanoe during the tertiary period in which these sedimentary 
beds were deposited in the freshwater lake of the Haute Loire. 
No alternation of volcanic matters with the sedimentary strata, 
such as those already described in the Limagne, have been 
detected within this basin. It is possible, therefore, that the 
earliest development of local volcanos occasioned such a dis- 
turbance as to cause the drainage of the lake ; on the other 
hand, several of the basaltic breccias, which we shall have occa- 



* X, Aymard mentions the following gracile, Monacmm vclmmwn. 
mammifera, as found by him in these f See Appendix. 

-Pataotheriumprimcevum, Pal, sub- 



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23 1^*Zl 'P ■■nH!P>.5, Chap. II. 



■» int 3-oesiMi if it A nrecg n e lake4nsm, 
i» iBtf awck. *iat mbrt *rf enptiow from 
^nhm j» ra jkhh& ^kf watts* ^wbr -viiiibr deawm off. 



17^ 3as«cr jr Sj!ft3bibcHw 
sir mr^eif -sxeit :£ii& juBwrEr. air am I acquainted 
wilt mr ittailt-j: ie^cnmun if ic fc ■jeeupfcs * TaDey-plain, 
ii>'Vt HI 1 "mi*- *- *m*r jv I 1 j in. T ajta. -anaawii between the granite 
jDit rn»* *» ram^-* jf "in* Fjtht ami At LyncsttB on the south, 
w**<t jmL i«aC jm£ A* pwrsirrrTr ^x-fe ani Devonian strata of 
die Tiraw. raruinpi -vnitii :ne L*he* imfc an cwftlet to the north. 
TV ttrtfaiy ^cafi* jt din? anah. 3avf so ciose a resemblance in 
•HbuartKr jdiI ;>*sni>u -viri time* :f :6e fcwer valley of the same 
nr*r ,ux>ut S»anne> .** u lead 3L Ranlia * to presume that the 
two aasmt wer»? gcannaZr ..nxmevterf by a channel permitting 
thtfor w*£-is *? niL : ntam die ata*? kveL The same red and 
t^ljjw floik Mmitcmesw days* and green and white foliated 
mads at* l-tnui AC MarvCIy. Rreo. Scnr le Comtal, and generally 
tap^OL^ot she plain* Several eruptions of volcanic matter 
aj-pear also to lave taken place within this basin, and from the 
graniti: he%tics to the west. Bat fcr the reason given above I 
am not a wan* of the precise circumstances under which the vol- 
canic rocks present themselves* 3L le Coq informs me that 
several basaltic dykes appear near the junction of the porphyry 
and granite; while others penetrate through beds of rolled 
pebbles, probably belonging to the lower term of the lacustrine 
series A further examination of this basin seems very desirable. 

V. Tbipou Basin of Mexat. 
At Menat, cm the road from Riom to Montaigu, occurs a sin- 



• Bulletin XIV. p. 584. 



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Chap. II. TEIPOLI BASIN OF MENAT. 29 

gular depression in the gneiss and mica-schist which here take 
the place of the granite of the primary or crystalline platform. 
It is nearly circular and about a mile in diameter, and discharges 
its waters into the Sioule through a narrow gulley worn in the 
schists not more than 12 feet wide and as many deep. Before 
this passage was effected they must have formed a lake over the 
whole valley, the surface of which is almost perfectly level 

The excavations that have been made in the sedimentary beds 
beneath this surface show them to be composed to a considerable 
but unascertained depth of bituminous shale, or desiccated flaky 
clay of a muddy black colour, evidently the fine detritus of the 
micaceous and talcose rocks which enclose the basin impregnated 
with bituminous matter, and often containing vegetable remains 
in such abundance as to become a true lignite. It envelops many 
nodules of iron pyrites, globular or lenticular, sometimes assum- 
ing the flattened moulds of fish, chiefly a cyprinus, very like 
the Cyp. papyraceus of the lignite of the Siebengebirge. The 
thin folia of the shale and lignite exhibit on their surface innu- 
merable impressions of leaves resembling those of the chesnut, 
sycamore, willow, lime, and aspen, which still grow in the neigh- 
bourhood, with others which certainly do not belong to European 
species, and resemble those of the liquid amber, Styracifiua and 
Gosaypium arboreum* Some flattened fruit* or seed-vessels, are 
also found resembling those of the hornbeam. These lignites 
appear to have undergone spontaneous combustion on some 
points (probably where pyrites abounded), and the shale has 
been thus converted into reddish tripoli, which is largely quarried 
for commercial use. It seems probable that the formation of 
this simple alluvial deposit is of no very distant date. 



* Bouillet, * Vuea et Coupes du Puy de Dome.' 



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» TCBU5HED 3OT1CES OS Chap. HI. 



CHAPTER IIL 

nrraoDrcTOET Accocyr of the notices which have been 

HITHEBTO PUBLISHED CONCERNING THE VOLCANIC REMAINS 
OF THE INTERIOR OF FRANCE. 

To those who now travel over ike mountains of central France, 
and see on all sides marks of volcanic agency exhibited in the 
most decided manner, numerous hills formed entirely of loose 
cinders, red, porous, and scorified as those just thrown from a 
furnace, and surrounded by plains of black and rugged lava, on 
which the lichen almost refuses to Tegetate, it appears scarcely 
credible that, previous to the middle of the last century, no one 
had thought of attributing these marks of desolation to the 
only power in nature capable of producing them. This apparent 
blindness is however very natural, and not without example. 
The inhabitants of Herculaneum and Pompeia built their houses 
with the lavas of Vesuvius, ploughed up its scoriae and ashes, 
and gathered their chesnuts from its crater, without dreaming 
of their neighbourhood to a volcano which was to give the first 
notice of its existence by burying them under the products of its 
eruptions. The Catanians regarded as fables all relations of the 
former activity of iEtna, when, in 1669, half their town was 
overwhelmed by one of its currents of lava. 

In the year 1751 two members of the Academy of Paris, 
Guettard and Malesherbes, on their return from Italy, where 
they had visited Vesuvius and observed its productions, passed 
through Montelimart, a small town on the left bank of the 
Rhone, and, after dining with a party of savans resident there, 



Chap. IH. THE VOLCANOS OP AUVERGNE. 31 

amongst whom was M. Faajas de St Fond, waited out to 
explore the neighbourhood. The pavement of the streets im- 
mediately attracted their attention. It is formed of short arti- 
culations of basaltic columns planted perpendicularly in the 
ground, and resembles in consequence those ancient roads in 
the vicinity of Home, which are paved with polygonal slabs of 
lava. Upon inquiry they learnt that these stones were brought 
from the rock upon which the Castle of Rochemaure is built* on 
the opposite side of the Rhone ; and were informed, moreover, 
that the mountains of the Yivarais abounded with similar rocks. 
This account determined the Academicians to visit that province, 
and step by step they reached the capital of Auvergne, dis- 
covering every day fresh reason to believe in the volcanic 
nature of the mountains they traversed. Here all doubts on the 
subject ceased. The currents of lava in the vicinity of Clermont, 
black and rugged as those of Vesuvius, descending uninter- 
ruptedly from some conical hills of scoriae, most of which present 
a regular crater, convinced them of the truth of their conjec- 
tures, and they loudly proclaimed the interesting discovery. 

On their return to Paris M. Guettard published a Memoir 
announcing the existence of volcanic remains in Auvergne,* but 
obtained very little credit The idea appeared to most persons 
an extravagance ; and even at Clermont a sagacious professor, 
who ascribed the volcanic scoriae to the remains of iron-furnaces 
established in the neighbouring mountains by those authors of 
everything marvellous, the Romans, gained far more partisans 
than the naturalist By degrees, however, the obstinacy of 
ignorance was forced to yield to conviction, and M. Desmarest 
some years afterwards, having published his ' Memoirs on the 



• Memoire but quelques Montagues de la France qui ont e*te* des Volcano. — 
Mem. de VAcad. des Sciences, 1752. 



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32 PUBLISHED NOTICES ON Chap. in. 

Origin of Basalt,' * accompanied with maps of many of the 
volcanic currents of Auvergne, put an end to all doubt upon 
the question. 

Faujas de St Fond, whose attention had by the circumstance 
above mentioned been directed towards the volcanic remains in 
his neighbourhood, published nearly at the same time his 
account 'Des Volcans eteints du Vivarais et Velay;' f but 
unfortunately, never having examined the phenomena of vol- 
canos in activity, or learnt to distinguish with accuracy the 
substances which have been produced or altered by this class of 
natural agents, fell into numerous errors ; mistook every chasm 
for a crater, every mass of basalt for a volcano, and saw nothing 
but decomposed lavas in beds of marl and sandstone. M. Des- 
marest's maps were astonishingly accurate, and evinced a very 
close and conscientious study of the localities. But his descrip- 
tive remarks contain many errors. He thought he saw, in every 
isolated fragment of an ancient basaltic current, what he called 
a culot, or residuum of lava stopping up the mouth of a crater ; 
and he entirely neglected all observations on the mineralogical 
characters and distinctions of the various lavas he discovered. 
The labours, however, of both these naturalists were of the 
utmost service towards the establishment of the fact — that 
numerous volcanos had broken forth in the interior of France at 
different and very remote period*, and had covered most parts of 
the provinces of the Auvergne, Velay, and Vivarais, with the 
products of their eruptions. 

Dolomieu likewise in the year 1797 passed hastily through 
Auvergne on his way to Switzerland ; but in the report which 
upon his return he presented to the Institute he makes but very 
brief mention of its rocks, and appears only to have sought in 



* Mdraoirea de l'Acad., 1771. t Fol. 1778. 




Chap. m. THE VOLCANOS OP AUVERGNE. 83 

them a confirmation of his favourite doctrine, the igneous 
fluidity of the central globe. 

Le Grand d'Aussy, in his * Voyage en Auvergne,' published 
in 1794, again called the attention of the public to the natural 
phenomena of this country, which were sinking into neglect ; 
but being more qualified for romantic descriptions than scientific 
observation, little real knowledge on the subject is to be gained 
from his work ; and it was only in 1802 that M. de Montlosier, 
after a profound and attentive study of the Monts Dore and 
Dome, published his Ess&y ' sur la Theorie des Volcans 
d'Auvergne,' and exhibited in their true light the various 
relations and distinct characters of these interesting volcanic 
remains. Desmarest, in his Memoir for 1771, had remarked 
that the perfect correspondence of repeated beds of basalt on 
each side of certain valleys demonstrates their having formed 
parts of the same currents, the continuity of which had only been 
interrupted by the excavation of the valleys subsequently to the 
flowing of the lava. Still he was far from applying this prin- 
ciple to its whole extent, and continued to look upon all the 
isolated hills capped by basalt, which are so numerous in the 
Auvergne, as so many volcanos denuded of their scoriae by 
currents of the sea, under which he imagined them to have 
burst forth; and enveloped by those horizontal beds of lime- 
stone upon which in reality the volcanic products repose. M. de 
Montlosier then was the first to establish the true nature of 
these basaltic peaks and plateaux, and thus gave a key to the 
study of the country, without which its phenomena would pre- 
sent a suite of interminable diificulty. Indeed, the greater 
number of his remarks have been received as established facts 
by all later observers, whose subsequent researches have but 
confirmed their solidity. 

M. de Buch, having paid a short visit to Clermont in 1802, 

D 



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34 PUBLISHED NOTICES ON Chap. III. 

wrote in a letter to M. Pictet an account of some of the meet 
striking volcanic remains in its vicinity, which was published 
immediately in the ' Bibliotheque Britannique,' together with a 
copy of a portion of Desmarest's map ; and in 1809 he printed 
in the second volume of his ' Geognostichen Beobachtungen ' 
some letters on Auvergne, accompanied by engravings of the 
Mont Dore, as an appendix to his ' Voyage en Italie/ &c 

In 1803 M. Lacoste, professor of Natural History at Clermont, 
published some observations on the Yolcanos of Auvergne, and 
in 1805 some letters on the same subject They contain, how- 
ever, little information of value. In 1808 M. Ramond, then 
prefect of the department of the Puy de D6me, read to 
the Institute his ' M^moires sur le Nivellement des Plaines,* 
to which was subjoined a list of heights measured barometri- 
cally in the neighbourhood of Clermont, and a compendious 
account of their geological characters. A short time after- 
wards, M. d'Aubuisson, who subsequently published a general 
treatise on Geognosy, laid before the Institute his observations 
made during a tour through the Auvergne, Velay, and Vivarais ; 
a tour, the result of which is well known to have been his speedy 
conversion from a thorough belief in the Neptunian origin of 
basalt and the other members of the floetz trap formation, to an 
entire conviction of their having flowed in a state of igneous 
liquefaction, and their complete identity with volcanic lavas — a 
conclusion to which indeed no one could fail to arrive who would 
pursue the same straight road to the truth as M. d'Aubuisson.* 

In 1815 M. le Baron Ramond presented to the Institute a 
second M£moire on the subject, entitled 'Nivellement Baro- 
metrique des Monte Dors et des Monte D6me,' which, besides 
the absolute heights of more than two hundred and fifty remark- 



* Journal de Physique, tomes 58, 59. 



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Chap. HI. T£E VOLCANOS OP AUVERGNE. 35 

able points upon these two groups of mountains, contains a 
detailed and methodical relation of their geological structure, 
drawn up with that scientific discernment and impartiality which 
have placed M. Eamond among the most distinguished observers 
of his age. To this work I have been much indebted, as well 
for a great body of local information as for nearly all the 
measurements of height I have made use of in the following 
pages. 

These, with the exception of a paper of Dr. Daubeny's in the 
* Edinburgh Philosophical Journal for 1820-21,' and a few 
scattered and partial notices inserted in the 'Journal des Mines,' 
by MM. le Coq, de Laizer, and Cordier, are the only writings I 
had met with on any of the volcanic remains of the interior of 
France at the time the first edition of this Memoir was published. 
Since that date the country has been again visited by Dr. 
Daubeny in 1830, and likewise by Messrs. Lyell and Murchison 
in 1829. The observations of the former are consigned to his 
volume on Volcanos (2nd ed., 1848). Those of the latter 
geologists were in part communicated to the public in the 
' Journal of the Geological Society ' (voL ii. p. 75), together 
with a paper in the ' Edinburgh Phil. Journ.,' April, 1829. Sir 
C. Lyell has since briefly and most ably sketched the geology 
of Auvergne, &c., in his ' Manual' Eeferences to the principal 
publications that have appeared on this subject from the French 
geologists are given below.* None, however, are of so complete 



* M. Rozet, Memoire sur les Volcans Paris, 1843. M. Passis, Bull. XIV., 

de I'Auvergne: Bulletin XIII., p. 221. p. 240, 1843. M. Pomel, Bull. XIV., 

MM. Le Coq et Bouillet, Vues, &c., du p. 206, 1843. Id., 2de Se>., i. p. 579, 

Departement du Puy de Dome, 1830. 1844. M. Provost, Bull. XIV., p. 125. 

M. Fournet, Ann. des Soc. Geol., i. M. Aymard, BuU. 2de Ser M vols, ii., 

p. 225, 1842. M. Ruelle, BuU. XIV., iii., iv. M. Bertrand Roux, Description 

p. 106, 1842. M. Raulin, Bull. XIV., du Puy en Velay, 1823— an excellent 

p. 547. M. Bnrat, Description des Ter- work so far as it goes. See also the 

rains Volcaniques de la France Centrale, Appendix to Daubeny 's Volcanos, 1848. 

D 2 



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8« PUBLISHED NOTICES, ETC.. Chap. III. 

a character as to serve the purpose of a general description of 
this very remarkable country, or as a guide to geologists who 
may wish to examine for themselves in detail its singular 
features, more especially that series of volcanic products which 
show themselves there in a variety of combinations and posi- 
tions of peculiar and perhaps elsewhere unexampled interest 
It is hoped consequently that the present publication may be of 
some service in that capacity. 



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Chap. IV. VOLCANIC FORMATIONS. 37 



CHAPTER IV. 

GENERAL ACCOUNT OF THE VOLCANIC FORMATIONS OCCURRING 
UPON THE ELEVATED GRANITIC PLATFORM OF CENTRAL 
FRANCE. 

i 

§ 1. It has been already mentioned that the volcanic formations 
of Central France attain an elevation much superior to that of 
the highest parts of the granitic platform. By many of their 
earliest observers, especially by M. de Montlosier, and subse- 
quently by Dr. Daubeny, they were described as of two classes, 
ancient and modern, according as they appear to have been 
produced before or after some supposed epoch of a diluvial cha- 
racter, to which the excavation of the existing valleys of the 
district was attributed. My observations of the general features 
of the country in 1821 led me not merely to doubt, but to deny 
altogether, that there is any reason for referring the denudatory 
action to which its valleys are due to any single cataclysm or 
diluvial phenomenon. It appeared to me clear that this process 
has been going on from the first appearance of the land above 
the sea — that it is still in action, being chiefly occasioned by 
the decomposition and erosion of rocks by rain, frost, and other 
meteoric agents, but especially by the direct fall of rain from the 
sky, and the wash of the superficial waters, which everywhere and 
on every scale of force, as rills, streams, and rivers, are cease- 
lessly engaged in sapping and mining their banks, and carrying 
off the detritus to the plains, which they cover with alluvium. 
This every flood drives further, and grinds still finer, until it is 
ultimately carried out in the shape of sand or mud into the sea, 



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38 VOLCANIC FORMATIONS. CffAP. IV. 

where it settles as a sedimentary deposit I thought I saw 
ample proofs in the relative position of the plateaux of basalt 
and trachyte which are seen capping so many of the hills in 
Auvergne at various elevations, some more than a thousand feet 
above the level of the plain of the Limagne, others but slightly 
raised above its surface, or the alluvial bottoms of its tributary 
valleys, that the excavation of these valleys, as well as of the plain 
into which they descend, has been gradual from the earliest to the 
latest times, and accompanied throughout by occasional volcanic 
eruptions, chiefly from the neighbouring gr&nitic heights, but 
sometimes from within the area of the lake-basin, that is, of the 
existing plain of the Limagne ; and consequently that no clear 
chronological line of separation can be drawn between the ancient 
and modern volcanic products ; although, no doubt, some are of 
a very remote antiquity as compared with others. 

It seemed to me, viewing as a whole the entire district of 
Auvergne, the Velay, and the Vivarais, that its volcanic rocks 
divided themselves geographically into six distinct groups, viz. — 
first, the three mountain masses of the Mont Dore, the Cantal, 
and the Mezen, each of which raises its colossal bulk from the 
granitic platform to a height of about six thousand feet above 
the sea, and appears to have been a centre of repeated eruptions 
on the largest scale, giving birth to a volcanic mountain like 
Etna, Teneriffe, and other sites of habitually recurring eruptions ; 
2ndly, the products of more isolated vents of eruption which broke 
out at various periods, but by far the greater number since the 
quiescence of the habitual volcanos above mentioned, upon a zone 
running nearly north-west and south-east from the north-west of 
Biom to the neighbourhood of Aubenas on the Ardfeche. Some 
rather wider breaks than usual between the points of eruption 
on this line induced me to divide this group also into three 
sections : 1, the chain of puys of the Monte Dome ; 2, that 



# 



Chap. IV. VOLCANIC FORMATIONS. . 39 

of the Haute Loire ; and 3, the cluster of volcanic vents of the 
Vivarais which tave broken out in some tributary gorges of the 
Ard&che. To these indeed should be added a fourth and inde- 
pendent group, which I have not myself examined, and of which 
I have not succeeded in finding any detailed description. It 
occurs south of the Cantal, near La Guiole, and on a line parallel 
to the eastern zone already mentioned. . 

The geographical convenience of this division seems to have 
led to its adoption by later writers, both French and English : 
I shall therefore continue to employ it in the following pages. 
But for many reasons — especially that it forms the first in order 
of approach to visitors from Paris and the north, and the best 
introduction moreover to the other volcanic phenomena of the 
district — I shall begin with the description of the chain of puys 
(as they are called) of the Limagne and the Monts D6me, which 
rise to the west of Clermont-Ferrand, the chief town of the 
department of the Puy de Dome, and an excellent centre from 
which to explore the remarkable country around. 



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40 V0LCAN0S OF THE . Chap.VJ 



CHAPTER V. 

FIRST VOLCANIC REGION.— MONTS DOME AND THE LIMAGNE 
ITAUVERGNE. 

The Limagne d'Auvergne, as has been already noticed on the 
subject of its freshwater formation, is an extensive valley-plain, 
about twenty miles in breadth and forty in length; its soil, 
with the exception of the calcareous hills already described, 
being an alluvium consisting chiefly of boulders of granitic 
rocks, trachyte, and basalt, through which the AUier for the 
most part still wears its channel in a course from south to north. 
The inclination of the surface of the plain towards the river on 
either side, where not interrupted by hills, averages perhaps 
twenty feet in a mile. This at least is its slope from the base 
of the low hill on which Clermont stands, to the low- water mark 
at Pont du Chateau, the first point being 1204, the last 1027 
English feet above the sea, and the distance about nine miles. 

The western limit of the plain is formed by the abrupt 
escarpment of the granitic platform already described, which is 
fringed by some lower hills that branch off from it into the 
plain, and farrowed by steep and short ravines. These on being 
explored are found to penetrate to no great distance, terminating 
at the base of the range of volcanic hills, or " puys" as they are 
locally called, which rise from the otherwise nearly level plateau 
in a line nearly due north and south. On the western side of 
this chain of puys the platform slopes more gradually towards 
the valley of the Sioule, which runs nearly in a parallel direc- 
tion. The width of this granitic table-land is about twelve 



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Chap. V. CHAIN OP PUYS, OR MONTS DOME. 41 

miles ; its average elevation 2800 feet, being about 1600 above 
the plain of the Limagne ; but on some points where it has been 
preserved from denudation by a capping of basalt it attains 3300 
feet On its western side it is composed chiefly of gneiss, but 
on the east of veined granite, in which transitions from a coarse 
to an extremely fine grain are very frequent Much of this 
rock readily decomposes, and every storm washes away heaps of 
crystalline sand from its exposed surfaces. Upon thia platform 
rises the " chain of puys," comprehending about seventy volcanic 
hills of various sizes, several of them being grouped together in 
immediate contact, in other cases a considerable interval inter- 
vening ; the whole, together "with the scoriae and volcanic ashes 
which cover the plain around and between them, forming a 
notched and irregular ridge directed north and south, about 
twenty miles in length by two in breadth.* 

With the exception of five (among which is the Puy de D6toe 
itself, the loftiest and most prominent of these hills), all of them, 
are volcanic cones of eruption,! apparently of very recent pro- 
duction. Their height is from 500 to 1000 feet above their 
base. They are generally clothed with a coarse herbage or 
heather ; some few with thick forests of beech, once much more 
abundant This covering, however, does not hinder an examina- 



• See Map of the Monts Dome, and into the vent are, of course, thrown up 
the profile sketches, in Plates I. and again and again, and triturated into gra- 
il, velly sand or fine ashes by the friction 

f A volcanic "cone of eruption" in attendant on this violent process. Those 

its normal form, with a "crater" or which fall on the outside of the vent 

cup-shaped hoUow at its summit, is the are heaped up there in a circular bank, 

result of the accumulation round the the sides of which, both within and 

Tolcanic orifice or vent of the scoriae without, slope at an angle rarely ex- 

and other fragmentary matters pro- ceeding 33°. And this liank, viewed 

jeeted into the air by the series of ex- externally, has of course the shape of a 

plosive discharges of elastic vapour and truncated cone, the crater being a hol- 

gases which usually characterises an low inverted cone contained within it. 
eruption. The fragment* which fallback 



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42 V0LCAN08 OF THE Chap. V. 

tkm of their composition, which is betrayed by frequent rents 
and scars in the turf. Many considerable portions seem to have 
been always bare of vegetation. 

They appear entirely and uniformly composed of loose scoria?, 
blocks of lava, lapillo, and puzzolana, with occasional fragments 
of domite and granite. Their form is more or less that of a 
truncated cone ; the sides rising at an angle which oscillates 
about 30°. The crater is often perfect, and the hill must then 
be mounted to observe it Frequently, however, it is broken 
down on the side whence the lava issued, evidently by the 
weight and impetus of this substance, when propelled from 
the volcanic orifice in a fluid state after the formation of the 
cone. 

In some instances eruptions have taken place on different 
points so near each other that their ejected matters have 
mingled ; and in place of a single cone, an irregular hill with 
two or three distinguishable craters, or a long-backed uneven 
ridge, has been the result One, the Puy de Montchi6, has four 
distinct craters, which, however, are not visible till the hill is 
mounted. 

It is probable that almost every one of these numerous vents 
has famished its stream of lava ; but the bases of the cones 
being sometimes partially cultivated or covered with forests, it 
is impossible in every instance to discover this; nor, for the 
same reasons, is it easy to trace to its source every visible 
current and ascertain the precise crater which produced it 

The volcano evidently sometimes continued to eject sconce 
. and ashes after the lava had ceased to flow — a circumstance 
often remarked in the eruptions of .Etna: in this case the 
immediate source of the stream of lava and its connection with 
the crater will have been concealed by these loose materials. 
Sometimes, it would seein (and this also is common to the erup- 






Chap. V. CHAIN OP PUYS, OR MONTS DOME. 43 

tions of all the recent volcanos I have had the opportunity of 
witnessing), the lava has been produced by one orifice, while the 
aeriform jets issued from another, the latter presenting an intact 
and complete cone of scoriae and fragments, the former a 
breached and imperfect one. 

In general, however, the currents of lava are observed to issue 
directly either from the crater or foot of the cone, and thence to 
spread over a wide expanse of the neighbouring plateau, or fill 
the bottom of a valley to some distance. Their surface presents 
a succession of shapeless and bristling masses of scoriform rock, 
and offers to the imagination the idea of a black and stormy sea 
'of viscid matter suddenly congealed at the moment of its wildest 
agitation. 

These fields of lava, which are either wholly bare or but 
partially clothed with stunted brush-wood, are called " Cheires" 
in the patois of Auvergne.* 

The lava has flowed either to the east or west according to 
the natural levels of the ground and the situation of the vent ; 
and though perhaps a larger number of currents have directed 
themselves towards the Limagne, entering some of the steep 
valleys which communicate with it, the gentle slope by which 
the plateau descends on the west to the Sioule has caused 
those which were poured out on that side to cover a wider space, 
and exhibit themselves in consequence more conspicuously .t 

A few eruptions have taken place, on either side, out of the 
principal line of puys. The most distant of these may be 

* It is «ngn1ay enough that the in- both words are derived! The serra or 

habitant* of the. fertile regions at the sierra of the Spaniards has a correspond- 

base of Mtns. should call their lava ing signification ; one of the basaltic 

rocks by a similar name, " Sciara" platforms of Auvergne is still called 

Borelli latinizes this, " Qlarea ; " but the and spelt La Serve . 

term "Serra" (saw), applied to the f See Plate II., and the Map of the 

jagged outline of a mountain range, Monte Dome, 
to be the common stock whence 



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rise 

aiatellDL. 



*•* ■ *• "— '■• ~ ■ ~ "z *" -frrrMK' -antx wnna»- 

- —» jlt - ~~-r . . *" — r • ifc — mr^siBr^ ">-?***iiDit* *ak!Ji 

- . * - «-a *-sa*i su> t- mh* **±n pinned 

~- . - _ -— _ tit — ib; . cjr msk »r sea* m 

i..r^r— w «* f -Of-*? ji ^ -jfcifie of 

- - -«— •• - ^ ::. ~—dL jrr»_—. fe* "mm. ^ t.'Oflifflui 

• -^ ^» - ir'%~ zztf s»n*- if -in? -frnptktts 

. ^ «* * * 3a r "' -omas ji**im*+ several 

^ .j*- — . : i — n f-:»— • -25**-*itr- ?W opened as 

^ ^ ,..--, ^^t — % ~ r i* iir Ian* &rces its 

- • .-^.i^ -I*-** _~*xr** *ih*r»? 5j dl> general 
-*.— - .* i -*. a* ->^l»-'— ^ lifcv* n.nn. a attaint hne 
^ ^ -»r nt*r-v r uuan^ -vmq in»»fvoktsely; 

^ ». **-^* - a-: ^** •»••. 

. ^. ... • l— ^ l ur *iaiii »t pays may be con- 

. — «, ^-%- . • -V.-.0-. «u *ii*** ii>? i*r :rvm belonging to a 

^- .i< c ■ ^':..:!i: *CTf<£ -hvir having: been thrown up 

,,... r ^ >UF.^»«a:ur «nf jat'ciier odea at dfctant periods. 

•.>••:. k*^-ss »i lit ir la -a-^urwnfcv some of which bare 

^** • a>iutnu.n^ ?u -\traai iewmpo^Goo, while the surface 

■iiinN > <i'lI \j*£>?* *iar>iu ^oii auiajored. woald not perhaps 




Chap. V. CHAIN OP PUTS, OR MONTS DOME. 45 

alone prove a sufficient criterion of age, since the power of time 
in producing these effects on lavas varies with their varieties of 
mineral constitution, the more or less of iron, felspar, &c, 
which they contain. The considerable dilapidation of some 
cones, and the elevated position of their currents relatively to the 
surrounding soil, are less fallible signs of a superior antiquity, 
more particularly where they coincide, as they invariably do in 
this district, with the former class of marks. 

Nothing, however, like an approximation to a knowledge of 
their positive ages can be expected, however interesting the 
elucidation of this question would be. All we know is, that, in 
spite of the very fresh aspect of many of them, their production 
must have been anterior to the earliest historical records of this 
locality, in which no mention is found of any volcanic eruptions* 

In the middle of the line just described rises the celebrated 
Puyde Dome, the Giant of the Chain, as it is called by Ramond; 
far superior in bulk and elevation to the numerous hills which 
stretch from ita base towards the north and south. Its height 
above the sea is 4842 feet, and about 1600 feet above its base, 
the sides sloping at an angle of from 30° to 60°. It consists 
entirely of that variety of trachyte which, from a supposed pecu- 
liarity of mineral character, has been named Domite. 

This mountain, with four or five other neighbouring hills of 
much less size, composed of the same rock, are so closely con- 
nected in situation with some of the volcanic cones of the chain 
of puys, in the centre of which they are found, as, notwith- 
standing their totally distinct structure and composition, to leave 
no doubt, in my mind at least, of their being connected likewise 
in origin with these cones, of their having been produced, in 
short, at the same time, and by a modification of the same 
volcanic agency. 

They are scattered irregularly amongst the other puys near 



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46 VOLCANOS OP THE Chap. V. 

the middle of the series, and are distinguishable from them at a 
distance by their whitish tint where the rock is exposed, and by 
their rounder contours. 

With the exception of {he Pay Chopine they consist entirely 
of that rock to which the most considerable of them has given 
the name of domite ; each appearing as one enormous mass of 
this substance, in which it is not easy to discover traces of any 
definite structure; in some parts nearly compact, solid, and 
moderately hard; light, earthy, friable, or completely pulve- 
rulent, in others. The substance' of one mountain differs but in 
accidental and insignificant characters from that of another. 
The colour of the rock is generally a greyish or brownish white ; 
but on many points it has acquired various tints of red and 
yellow from the action of acid vapours. It absorbs moisture 
with the greatest avidity, and this action is accompanied by a 
hissing noise and a considerable disengagement of air-bubbles. 
Its texture is rudely granular ; and on examination with a lens 
it appears to be an aggregation of imperfect microscopic crystals 
of glassy felspar, sprinkled with still smaller grains of augite, 
and occasional pallets of mica. These elements are partly 
separated from each other by minute pores, which render the 
substance rough, to the touch, light, spongy, and bibulous. The 
larger imbedded minerals are, the glassy variety of felspar, 
generally cracked and mealy ; mica in hexagonal or rhomboidal 
pallets, either bronzed or black ; hornblende in acicular hexagonal 
foliated crystals, generally of a deep black, and highly lustrous 
along the planes of cleavage ; and sphene ; as well as specular 
and titaniferous iron in dispersed grains, blade-shaped laminae, 
or regular octahedrons. 

That these different substances crystallized nearly at the same 
period, would seem from the intimate manner in which their 
crystals are interwoven. Yet in general it appears that those 



Chap. V. CHAIN OF PUYS, OR MONTS DOME. 47 

of mica and hornblende were entirely formed before the complete 
crystallization of the felspar ; for perfect crystals of both these 
minerals may be frequently seen enveloped or as if suspended 
in the centre of a large crystal of glassy felspar, and the cracks 
produced in the mica or hornblende are invariably penetrated 
by felspar. Very commonly the component crystals appear to 
have been broken, bent, or split,' probably by the movement 
which the enveloping substance suffered when propelled upon 
the surface of the earth from the volcanic focus. 

This rock is extremely liable to decomposition, which affects 
it often to the depth of some feet Its parts are then disaggre- 
gated, it assumes an earthy aspect, and crumbles between the 
fingers ; the crystals of felspar become carious, lose their lustre ; 
and finally the whole mass is resolved into a meagre and ashy 
powder, in which the crystals of hornblende, mica, and octohedral 
iron are found uninjured. 

The volcanic nature of domite has never been contested ; and 
indeed it is sufficiently evidenced by the pumice-stones which 
accompany and are enclosed by it ; the vitreous nature of its 
crystals of felspar; by its being porous, impregnated with 
muriatic acid, coated with sulphur, with sublimations of iron, &c, 
not to mention its similarity to the trachyte of the Mont Dore, 
which has still stronger proofs of a volcanic origin. 

Surrounded and partly embraced by cones of scoriae and 
lapilli, and remote from the rocks of the Mont Dore, which alone 
they resemble in substance, these hills have offered a perplexing 
problem to all the cursory visitors of Auvergne, and at the same 
time an ample field for conjecture to theorists. Hence the con- 
tradictory opinions that have been started on their origin. 
Desmarest considered the rock which composes them as a 
granite calcined in situ by a volcanic conflagration environing 
it ; — Saussure, a petrosilex which had undergone the same ex- 



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Chap. V. CHAIN OF JfUYS, OB MONTS DOME. 411 

warranted in the attempt, to account for its production by any 
other mode of formation than that which appears common 
to similar rocks in other places; unless such an explanation 
should be in this instance opposed by any manifest impro- 
bability. 

There is every reason to conclude the trachytes of the Mont 
Dore and Cantal, as well as the clinkstone of the Mezen, to have 
been propelled from a volcanic orifice in a state of incomplete 
liquefaction — in short, as lavas — and to have followed the incli- 
nation of the ground they occupied, flowing in a manner differing 
only from that of basaltic lavas in proportion to their different 
consistence and very inferior fluidity, or the accidental circum- 
stances which may have concurred to modify their disposition. 

It is evident that, under similar circumstances of the surround- 
ing levels and of propulsive force, the tendency of a mass of 
lava to quit the neighbourhood of the orifice from which it is 
emitted will be in exact proportion to its fluidity ; and when the 
fluidity is at its minimum, it will accumulate immediately around 
the orifice ; one layer of the half-congealed and inert substance 
spreading over that which preceded it, till the whole assumes 
the form of a dome or bell-shaped hillock perforated in the 
centre by the chimney or vent, through which fresh matter may 
continue to be expelled, but which will at the end remain closed 
by that last sent up. Now the variety of trachyte which com- 
poses the Puy de Ddme and the neighbouring domitic puys, 
consisting almost wholly of felspar, and therefore possessing the 
lowest possible specific gravity, and at the same time a very 
rude and coarse grain and highly porous structure, is precisely 
that species of lava which we should expect a priori to have 
possessed the minimum of fluidity when protruded into the air ; * 

* See Considerations on Volcaiiog, p. 92-96. 



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50 VOLCANOS OF THE Chap. V. 

and we therefore can understand perfectly why, instead of 
flowing in thin and continuous sheets or streams to a distance 
from its vent, like the basaltic lavas produced about the same 
time and from the same fissure, it has accumulated in dome and 
bell-shaped hillocks on the point where it was emitted. That 
this wa» the mode of production of these masses of trachyte, 
certainly that they were thrown up on the spots they now 
occupy, seems to me proved by their rising in every instance 
either from the middle or the side of a regular crater and cone 
of scoriae.* 

If it could be imagined possible for the volcano of the Mont 
Dore to have sent forth a vast current of trachyte in this direc- 
tion, of which these hills have been supposed the remaining 
segments, in spite of the fact that the great elevation of the 
granite ridge upon which they rest above the surrounding country 
renders it the last of all directions which such a current could 
have taken, and in spite of the improbability that a rocky bed 
of which the Puy de Dome, a mass rising 1600 feet above its 
base, is merely a detached remnant, should have left no traces of 
its existence in the interval between that mountain and the 
Mont Dore, a distance of 7 or 8 miles ; yet a still stronger objec- 
tion to this hypothesis remains behind, via. the improbability 
that the position of each of these fragments should severally 
coincide exactly with that of the vent of a separate recent 
eruption ; that the only points on which any considerable rem- 
nants of this supposed bed are to be found should be precisely 



• Set Plate III., and the map of the of eruption. The reaemblanoe of this 

Monta Dome. In Iceland M. Robert to the Puy de Dome, rising from the 

describe* ('Voyage en Islande,' Paris, crater of the Petit Puy, is complete. 

1840) the Mont Baula as a pyramidal In Hungary also, and elsewhere, tra- 

douie of yellowitth-white very porous chytic domes are described as rising in 

trachyte, partly columnar, at the foot the middle of crateriform hollows, 
of which is seen a contiguous crater 



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Chap. V. CHAIN OF PUYS, OR MONTS DOME. 51 

those on which, from the disturbance occasioned by the volcanic 
explosions, there is good reason to suppose it would have been 
destroyed and carried off. 

The theory of Von Buch evidently approaches more nearly to 
this explanation than that of d'Aubuisson and RamoncL Yon 
Buch supposes the domite to have been " granite liquefied by 
volcanic heat : " I also conceive it to have been, like all lavas, 
a mass of granite, or some congenerous crystalline matter, 
which, while confined beneath the superficial rocks at an intense 
temperature, was suddenly allowed to expand, by the giving way 
of the overlying rocks, and was consequently liquefied, or so far 
softened by the immediate generation of highly elastic fluids, 
both gases and aqueous vapour, through every part of its texture, 
as to be protruded, by the tumefaction incident to this process, 
through the clefts of the crust above. 

The part of Von Buch's theory with which I agree the least 
is his supposing these hills to be hollow, and blown up like a 
bladder. I imagine, on the contrary, the aeriform and highly 
elastic fluids, the expansion of which elevated the lava, to have 
remained chiefly where they were generated, viz. in a state of 
uniform and intimate dissemination throughout the texture 
and between the crystalline particles of the porous and elastic 
mass; and not by any means to have .united into one great 
bubble or dome beneath an overlying crust of the lava, as 
is implied in Von Buch's theory — a theory which Humboldt 
has adopted and applied, with some rashness, to all trachytic 
formations. I need not dwell any longer on this topic, as the 
laws by which I conceive trachytic, as well as other lavas, to 
have been determined in their rise and appearance on the sur- 
face of the earth, have been developed in detail in another work 
(' Considerations on Volcanos,' pp. 8.5-129) ; and that the peculi- 
arities which distinguish these particular trachytic formations 

E 2 



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-^ -r a I-ui^ I n=: 1=1 r ? *ii*iai T^zmensir * ia? *> reference 
a "i^ ^-^r-s. ;»2^- :<r~ ^ aerr~ t*i rvm. :£*» wvofe with which it 
»^&> * rsptx-- ■] ?nt*L Aaii ae rem.*ry cf wiirh still carer the 
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* >** da.' *f -u* X ts IX=j*. .^aerally to cvtMirm my own obeerva- 

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- :wz-v: w- i 11 o *f rVs~-.fcre*:. »ij«:i t^Ai I townar a st instated on seeing a 
Eu-ri« la'* *5s^:<*i =j« - '- -* ; c r =J- *" calot ** or dyke of eruption in every 
mt*=lt tic rw - I t*T* ic =d tbe Lttter drt*cned fragment of a batalt current. 



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Chap. V. PUY DE DOME. 53 

consistence of its substance, which resists decomposition and 
atmospheric erosion much more in some parts than in others, 
two sides are, as well as the summit, entirely covered with thick 
grass, and present a smooth and gently curved outline, while 
that of the others is broken by rocky projections, giving them an 
aspect of a ruder character. The fissures of the harder portions 
of rock are lined both with laminar and octohedral crystals of 
specular iron ; those of the more friable and earthy with similar 
sublimations, which in these points assume the brightest tints of 
blue and green, and occasionally with a coating of sulphur. The 
substance of the rock itself is in many places frequently stained 
throughout with varying shades of an ochry yellow, citron, 
rose, scarlet, and greyish-blue colour. Fragments of domite 
thus tinged, when rubbed together, give out a strong smell of 
muriatic acid, and M. Vauquelin has detected in them the 
presence of this acid by analysis. The exhalations to which 
these effects must be attributed were probably evolved through 
crevices from the interior of the mass of trachyte during the 
process of cooling, and were the result of the partial decomposi- 
tion of its inner substance by intense heat, as the elastic vapour 
•it contained escaped through the pores of its outward surface, 
and thus diminished the pressure which had before opposed the 
decomposing influence of heat* 

A chapel was anciently erected on the summit of the Puy de 
Dome, of materials brought from a distance (the additional 
labour «nd expense incurring of course a redundancy of gratitude 
from Our Lady, to whom it was dedicated) ; and the ruins of 
this building have probably strewed the sides of the mountain 
with the blocks of basalt which are occasionally found there. 
The scoriae occurring in the same situation have been evidently 

• See Considerations on Volcanoa, p. 1 2."»-U. 



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54 MOXTS DOME AND LTMAGXE. Chap. V. 

projected there by the explosions of die neighbouring cones. 
Ex^^Miin^ly !i*rht and parens fragments of domite, Tt»f»emWinjr 
pumice in these characters and in their indent to the touch, 
bat without its very vitreous filaments also form part of the 
loose ddbris of tills mountain, and many of them, appealing 
to have been rounded by attrition, may be observed -imbedded in 
the more solid rock. 

It is difficult to discover anything in the structure of the Puy 
de Dome to indicate the particular mode of its production. I 
have given above the general conclusions to which I have arrived 
with reference to this as well as the other tmchytic hills of the 
chain. On the south side the base of this mountain has been 
perforated by volcanic explosions, which in all probability imme- 
diately succeeded the protrusion of the trachytic lava, and which 
have left a large crater, half-encircled by abrupt cliffs of trachyte, 
and containing within it a complete cone composed of frag- 
mentary trachyte, scoria?, and lapOlo. This cone is called the 
Puy de Besace (39), and the ridge of the surrounding crater the 
Puy de Gronianaux (38), On the north side of the Puy de 
Dome, and immediately contiguous to it, is another crater belong- 
ing to the Petit Puy de Dome, to the description of which wtf 
proceed. 

Chain of Puts korth of the Puy de Dome* 

1,* Petit Puy dc Dome*— A volcanic cone, one of the largest 
though not the most perfect of the chain, leans against the 
northern flank of the Puy de Dome. Viewed from a distance, it 
appears to be a dejiendence of tliis latter mountain, and hence 
the name it has received of Le Petit Puy de Dome. Upon a 
closer inspection the different nature of the materials of the two 



* The numbers re for to those <m the mnj> of thft chain. 




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Chap. V. PUYS NORTH OF PUY DE DOME. 55 

mountains is immediately apparent ; the Petit Dome being com- 
posed entirely of fragmentary matter, basaltic scoriae, sand, and 
ashes. This volcanic cone reaches an elevation of 4186 feet, 
and is lower by 656 feet than its colossal neighbour. 

It contains a very regular crater, shaped like the interior of a 
deep bowl, and called by the mountain herdsmen " Le Nid de la 
Poule," " The Hen's Nest" Its diameter and depth are nearly 
equal ; the latter measures 300 feet from the highest point of 
the circumference, of which the southern portion is much the 
lowest To the north and east an outer semicircular ridge, 
running parallel to the inner one, appears to be the rim of an* 
older crater defaced when that now existing was formed. 

From the western base of this hill a stream of basaltic lava 
called the Cheire de VAum&ne takes its rise, and extends to a 
considerable distance over the slope of the granitic platform, but 
is at length lost under a cultivated soil, t>r confounded with 
other and seemingly later currents, which have taken a similar 
direction. This lava was most probably emitted at the epoch of 
the eruption of the Petit Ddme. 

2. The Cheat Suchet — a saddle-shaped eminence with some 
slight traces of a crater on its southern slope — is connected with 
that last described by means of the Little Suchet (63), one of the 
domitic hills, which stands at the point of a right angle formed 
by the ridges of the hills it unites. The fragmentary matters 
that compose the Great Suchet were apparently projected by the 
same eruption which produced that mass of trachytic lava ; and 
this idea, suggested by their proximity in position, is confirmed 
by the numerous blocks of domite and pieces of pumice which 
enter into its composition. 

3. Puy de Come. — Rather to the west of the meridian on 
which stand most of the puys, rises that of Come, remarkable for 
the regularity of its conical form ; for its height, exceeding 900 



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_: _• _j— .. .^i - ?i i-» 5T— t>- j*~* -lyjmayivd an 
_j_- .1." r- — .--^*j--r : jr^— Tsr. ¥n-d -t*jmdt •-awed the 
■^r*.- - -^-^ - ~^ r^*ar* Iiac a- dfcr rirfu. the 
.. -* • _-». --• - - -ur *-*■ * ~cr»«»i jhciI •**« a TOrt nriace. 
^. w ^^-w ■ ~r*- j-a-.-a- ^.JBDa i our zanifer platform, 
_-^j-.. -v ^r^ ** t.- *-=« ^11 .t n obi an vbiaaele in a loop 

. • ^s^cil^ : *Ji~»i adF ±\b* die Moot Pore 

» — ,. ■ u: ^ -r -»r*^a t 'mau! Hub impeded in hg 
-» u — ^ -ue- ^ -i : _ -i— i "i** **w~~p •* d*e hill in a north- 
■ifrt -^r*^ ': -i »^-~ ~ *^ ** -J^oe at Length between this and a 
^tui-av c; J %— a i. ^raTr^i :» pnxrrew towards the north, 
*» *r— . i* *n a -s.r *r* -^ur *«e "t die castle and town of Pont 
• -. -atiu. ■m.m?»ii»&--y *o«'V? which it seems to haTe met and 
i. A-*i 'V* r j out*? aarifut itivam from the Puy de Loucha- 

lit.""- N*». — * - 

Pieuce b»»tii ti»trether poured in a broad sheet of laTa down 
the >re**p >i*ie *>f a granitic hill which formed the eastern border 
of the vaiie v of the Sioale. dashing forward against the rocks on the 
opposite side, and usurping the channel of the river, down which 
thev pursued their <»onrse to the distance of more than a mile. 



Chap. V. 



PUYS NORTH OF PITY 1)E DOME. 



57 



The Sioule, thus dispossessed of its bed, has been constrained 
to work out a fresh one between the lava and the granite of its 
western bank, which in consequence is extremely precipitous. 
But, before this was accomplished, there is every appearance of 
its waters having been so far obstructed as to create a lake, 
covering the flat and alluvial surface now forming the meadows 
of Pont Gibaud. 




Rock of Prismatic Lava on the Bonk* of the Simile, near Pont Gibaud. 



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58 MOXTS DOME AND LIMAGNE. Chap. V. 

In one part of this new channel, where the valley has a slight 
bend, and the torrent of lava being opposed by a salient rock 
accumulated to a considerable thickness, the excavation effected 
by the river has disclosed its internal division into vertical 
jointed columns, the lower portions of which are straight and 
well formed, the upper twisted into various curves, and less 
regularly polygonal The wall of lava is about fifty feet high, 
and the columnar division is prolonged incompletely to the extent 
of between 200 and 30ft yards. (See the woodcut overleaf.) 

The rest of the lava filling the valley where it is about the 
third of a mile in breadth, is split by fissures, mostly vertical, into 
amorphous masses which still at various points evince a ten- 
dency to the prismatic form. This is perhaps the most marked 
instance of all Auvergne in which the lava of one of the very 
recent volcanos assumes a decided columnar division. In the 
Vivarais, as will be seen in a future chapter, this circumstance 
is of frequent occurrence. 

The sketch (Plate II.) was taken from a basaltic plateau on 
the summit of the granitic range of hills, west of the Sioule, 
from whence the greater number of puys may be observed; 
that of Cdme being the most conspicuous as well as the nearest 
The whole course of this branch of its lava, as well as that of the 
Pay de Louchadiere, is seen from this point 

But the Sioule was not to suffer from this invasion alone. 
The other branch of the lava-current of C6me, called the Cheire 
de l'Aumone, which flowed on from the point of separation in a 
direction west-south-west, soon reached the bed of this river, about 
three miles above the spot of the other irruption, and pouring over 
its banks filled up the entire valley with an immense causeway 
more than 100 feet high. Exhausted by this effort^ it pro- 
ceeded but a short way down the bed of the stream towards the 
north, and stopped where the village of Mazayes now stands. 



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Chap. V. PUYS NORTH OF PUY DE DOME. 59 

• 

The baffled waters of the Sioule here, as at Pont Gibaud, 
obstructed by the rocky dyke thus suddenly thrown across their 
channel, must have given birth to a lake by their stagnation, 
and would probably have ended, as in the other instance, by 
wearing away a passage parallel to their former one, had not 
the hill forming their western bank, not in this instance com- 
posed of granite, but of a soft alluvial tuff, yielded, at some 
distance up the stream, to the excessive pressure of the dammed- 
up waters. An immense excavation, still subsisting, was broken 
across this hill, through which the lake emptied itself into the 
bed of the Monges at no great distance, and through which the 
Sioule still joins this latter stream about three miles above their 
former confluence. 

A considerable body of back-water still remained behind in 
the part of the valley of the Sioule intercepted between the 
dyke of lava and the emissory thus forcibly created, which, 
from the inclination of the ground to the north, could not vent 
itself by this opening ; and here a stagnant piece of water called 
the Etang de Fung, and used by the Seigneurs of Pont Gibaud 
as a stock-pond, existed till within a few years, when its drainage 
was artificially effected The high banks which rise on each 
side of the long marshy meadow now occupying the site of the 
old pond still present the correspondence of angles so generally 
observable along channels of running water. 

On the opposite side of the enormous causeway of lava to 
which this diversion is owing, another small piece of water, 
occupying the bed of a tributary rivulet choked up in the same 
manner, is dignified by the name of the Lake of Mazayes, and 
its insignificant drain now runs into the Sioule through the re- 
mainder of the wide and deep valley which this river itself once 
excavated and possessed. . 

The changes thus effected do not only present themselves to 



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60 MOOTS 1H)ME AND LIMAC.NE. Cha*. V. 

• 

the eye of a nice ol)server, but are exhibited in a manner not to 
be mistaken by the most casual; and in fact they result m> 
simply and necessarily from the causes brought into action, that I 
should not liave dwelt so long ujxm their details, but that they 
serve to exemplify the mode of formation of other lakes in 
the Auvergne and Velay, and the origin of other changes 
in the surface of a country or direction of its rivers, where 
every link in the chain of causes and effects is not quite so 
palpable. 

The whole superficies of the plateau covered by the lava of 
CAme cannot be estimated under ten square miles. Its thickness 
is not to be ascertained, since no excavation has been made 
through it; where the current has met with any olwrtacle, it 
must of necessity l>e considerable, and thirty feet may be taken 
as the probable average. 

It is one of the most nigged Oheires of the Monts Dome, pre- 
senting a succession of continual asj>erities, following one another 
like the waves of an ocean, with similar depressions between. 
Upon walking over its surface, — no easy task, — it appear? to 
consist of cliaotic heaps of rocky and angular blocks of compact 
Iwisalt, tossed together in every variety of disorder ; yet, in the 
deep and narrow intervals l>etween th<*se heaps, occur little 
[Mtches of fresh and flowery turf, and knots of underwood spring 
from their clefts, contrasting strangely with the horrid desolation 
which prevails over this extensive wilderness. 

Near the limit of the northern current, at some distance from 
Pont (liltfiud, is a natural grotto in the Imsalt ; from its interior 
gushes a small spring, which is {tartly frozen during the greatest 
heats of summer, and is said to lie warm in winter ; probably, 
however, only seeming warm by contrast with the external 
temjterature. 

The water is appuvntly frozen by means of the powerful 



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Chap. V. PUYS NORTH OF PUY DE DOME. 01 

evaporation produced by a current of very dry air issuing from 
some long fissures or arched galleries which communicate with 
the cave, and owing its dryness to the absorbent qualities of the 
lava through which it passes. This is a phenomenon common 
to caverns in other volcanic districts. 

The basalt of the Cheires de Come and de l'Aumone is almost 
identical in its mineralogical characters ; it is replete with irre- 
gular cellular cavities, is of a dark greyish-blue colour, and 
contains a notable quantity of felspar. It is sufficiently tough 
to be worked for building-stone, and cuts well under the chisel. 
Nodules of pure white quartz are not unfrequently found en- 
veloped by it, appearing to have suffered from heat only on the 
surface, which is cracked ahd sometimes shows a commencement 
of fusion. 

4, 5. Puys de Barmet and Filhou. — Two small cones, the last 
of which has a semi-crater well marked out ; that of the former 
is nearly effaced. These two hillocks were probably thrown up 
from side apertures at the epoch of the eruption of the Puy 
de C6me. 

6. Puy de Pariou. — From its aspect, and that of its lava, this 
puy may be supposed the product of one of the last eruptions 
which convulsed the country. It is also one of the most con- 
siderable and regular cones of the chain. 

A segment of an older crater half encircles it on the north, 
and here the process by which this and similar hills have been 
produced is manifest The aeriform fluids developed in the 
interior of an ebullient body of subterranean lava, having by 
their expansive force effected a fracture in the overlying rocks, 
struggle upwards in powerful bubbles through this aperture, 
carrying with them at every eructation showers of scoriae and 
their comminuted fragments. These accumulate round the 
margin of the orifice into a hill, necessarily approaching more 



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_ 



«2 MONTS DOME AXD LIHAG^E. Chap. V. 

or leas in figure to die solid which would be generated by the 
revolution of an obtuse scalene triangle round one of die angles 
of its base ; and this bill i* called a volcanic cone, which, it 
must not be forgotten, when most perfect, is but a truncation of 
the geometrical one.* 

Bat when die intumescent lava itself has subsequently risen 
and poured itself forth from the same Tent, it must by its 
weight and impetus generally beak down and carry away part 
of the loosely built hQl encircling the aperture, and a semi-cone 
only then remains, the crater appearing open on one side. If 
the lava escapes from some other orifice, or by some channel 
U: neath the foot of die cone, and does not rise within the crater, 
a complete cone is the result, haying a perfect crater at its 
MfemrL 

After die lara has ceased to be emitted, or has established 
another channel for its efflux, the gaseous explosions still usually 
continue for a certain time, by which a second cone is formed. 
This in the absence of subsequent disturbing causes remains 
perfect, as has happened in the example of the Pay de Pariou 
now under consideration, where since the first outburst of its 
vast current of lara the volcanic mouth evidently threw up pro- 
digious showers of scorue and puzzolana, creating the beautiful 
cone and.crater of Pariou upon the brink of that which had been 
termed by the earlier explosions of the eruption. 

rhis newest crater has the figure of an inverted cone. It is 
clothed to the bottom with grass, and it is a somewhat singular 
spectacle to see a herd of cattle quiedy grazing above the orifice 
whence such furious explosions once broke forth. Their tracks 
round the shelving sides of the basin in steps rising one 
above the other, like the seats of an aihphitheatre, make the 

* See note to p. 41. 



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Chap. V. PUTS NORTH OF PUY DE DOME. 63 

excessive regularity of its circular basin more remarkable to 
the eye. 

Its depth is 300 feet, and circumference 3000. The inclina- 
tion of the sides of the cone and of the crater are both about 35°. 
The acute ridge resulting from their junction is so little blunted 
by time, that in some parts it scarcely affords space to stand on. 
Its highest point is 738 feet above the southern base of the puy. . 

The lava of Pariou is as instructive with regard to the circum- 
stances which accompany the movement of this substance in 
viscid torrents over a large tract of country, as its cone on 
those- by which such mountainous excrescences are suddenly 
thrown up. 

Its first direction is to the north-east, and the current appears 
to have set strongly against a long-backed granitic eminence 
opposing it on that side. Thence, led by a considerable slope 
towards the south-east, it coasted the base of this hill ; and leav- 
ing to the right another protuberance of the primitive plateau 
on which now stand the church and hamlet of Orcines, advanced 
to a spot called La Baraque. Here it met with a small knoll 
of granite capped with scoriae and volcanic bombs, marking the 
source of a much more ancient basaltic bed known by the name 
of Prudelles. Impeded in its progress, the lava accumulated on 
this point into a long and elevated ridge, which still bears the 
appearance of a huge wave about to break over the seemingly 
insignificant obstacle. But an easier issue offered itself in two 
lateral valleys having their origin in the part of the plateau 
occupied by the lava-current ; which, separating consequently 
into two branches, rushed down the declivities presented on 
either side. 

The right-hand branch first deluged and completely filled an 
area surrounded by granitic eminences, and probably the basin 
of a small lake ; thence entered the valley of Villar, a steep and 



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04 MONTH DOME AM) L1MAUNK. CHAf. V. 

sinuous gorge, which it threaded exactly in the manner of a 
watery torrent, tinning all the projecting rocks, dashing in 
cascades tlirough the narrowest ]>arts, and widening its current 
where the space permitted, till, on reaching the einlHmehure of 
the valley in the great plain of the Limagne, it stopped at a 
spot called Fontmore ; where its termination constitutes a rock 
alx>ut .50 feet high, now quarried for building-stone. From the 
base of this rock gushes a plentiful spring, the waters of which 
still find their way from Villar beneath the lava which nsuqied 
their ancient channel.* 

The branch which separated to the left plunged <k>wn a steep 
bank into the valley of Gresiuier, replacing the rivulet that 
flowed there with a black and shagged current of lava ; euterwl 
the limits of the Limagne at the village of Durtol ; and con- 
tinuing the course marked out by the streamlet, turned to the 
north, occupied the bottom of the valley lying lietween the 
calcareous mountain Les Cotes and the curtain of granitic roeka, 
and finally stopped on the site of the village of NohanenC 
Here, as at Fontmore, an abundance of the purest water springs 
from below the extremity of the lava-current The various rill* 
which drain the valley of Durtol and itw embranchments, have 
rtM'overed their pristine channel, and, filtering through the scuri- 
form masses which always form the lowest surface of a bed of 
lava, flow on unseen, till tin* rock alx>ve terminates, and they 
issue in a full and brilliant spring. Al>ove this point, conse- 
quently, is seen the anomaly of a valley without any visible 
stream ; and the inhabitants of Durtol are condemned in seasons 
of drought to the strange necessity of seeking at Xohanent. a 
distance of two miles, the water which flows there beneath their 



• The*e and tho other la\A-curn'iit« of the th.iin of |iii>» or\- .til u> U* tr**t*1 
(Hi the iuu|» of the Molitu Duuie. 



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Chap. V. PUYS NORTH OF PUY DE DOME. 65 

own houses. A similar phenomenon is very general throughout 
the Auvergne, wherever a current of recent lava has occupied the 
bed of a mountain rivulet, not sufficiently copious or violent to 
undermine the lava above, or open a new side channel through 
its former banks. 

In its appearance the Cheire of Pariou is even more bristling 
and rugged than those already described. M. d'Aubuisson 
justly compares it to a river suddenly frozen over by the stop- 
page and union of immense fragments of drift ice. 

In the work to which I have occasionally referred on the 
general laws and conduct of the volcanic forces,* I suggested that 
this asperity of surface in a lava^jurrent is probably owing, and 
appears usually proportioned, to the high specific gravity of the 
lava, which determines the ascending force of the bubbles of 
vapour that, expanding in its interior, rise, and escape from the 
surface as it flows onward. The lava of Pariou, which is com- 
posed almost wholly of augite, and therefore of high specific 
gravity, confirms this law. The same circumstance accounts for 
the other characteristics of this rock, which is perfectly compact 
in the interior of the current, while the outer portions are cellular 
and cavernous. The cavities, often of large dimensions, are 
lined with a dark vitreous varnish, and from their sides project 
numerous stalactitic protuberances, and slender filaments, coated 
in the same manner. 

The colour of this basalt is a deep shade of bluish-grey ; it 
contains imbedded crystals of augite, and a few of glassy felspar, 
and bears a great resemblance on the whole to the current from 
the Monti Rossi, which in 1669 destroyed a part of Catania; and 
reached the sea. 

* Considerations on Volcano*. London: Phillips, 1825, pp. 119-20. 

F 



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* 3D 5TS I« SE AST' LTMAGX1L Chaf. V. 



It w it *Z pr cwruity a* eruption of the Pay de Parioa 
wiiA fiww ^ icm* j*t^* Areamaattioag of pmaolana that are 
ckerrabie en Kci ais ct tse granitic ridge of Ternant and 

7. /\* id J^c**. — F^cweea £e Pets of Parioa and Cdme 
lies tbtf :i Praise, a sadiiLe-^ipeii hiZ. deToid of any peculiar 
interest exwct 2btt r^^fea&I-^e jit*. wiiA is seen only in erratic 
tix-kv ci5ets fern £as :t :£e Pits already described by coii- 
ta:r.:r.g crystals of ccvizi*. 

64. CZ*fr*m* — T^i> ray oecr^ses the centre of an area fanned 
by the &cor Tv^jAr.a- cvces^ PiriciL. Le Grand Sachet, Come, and 
La Fraksei. It? fesre is imcet precisely that of a bell, as the 
ecOTavfcsg will sbcw.* T^irf asd bna&wood corer the swelling 
carve of its s*eep st&»s. aal a ring of broken rocks ferns the 
edge of the circular aai iiKkh tapping which crowns it This 
capping appe**rs to be rccLiras of an octer envelope, the lower • 
puts of which have been wvni away. The whole substance of 
the hUl is a liLit and pcroos trachyte* differing in nothing from 
some parts of the Put de Poeie. The upper half of the hill is 
perforated in all directions by raves and galleries formerly 
pierced foe the extraction of this stone, which is supposed to 
have been held in esteem by the Soman colonists as a material 
for sarcophagi, in consequence of its jwoperties of absorption. 
These cares abound in fragments of pumice detached from their 
walls, in the substance of which much of this mineral is observed 
to be enveloped. Pumice we know stands in the same relation 
to trachytic rocks as scoriae to basalt and these pumiciform 
parts are created of course in the former rock by the same local 
and accidental development of gases which occasion the 

• See Plate III. 



18 Ie 



Chap. V. PUYS NORTH OF PUY DE DOME. 67 

extremely cellular and scoriform parts often found in the sub- 
stance of the latter. 

M. Eamond supposes Cliersou and Le Petit Suchet to have 
been united formerly ; and indeed this follows of course from his 
theory as to the origin of all these domitic hills from the Mont 
Dore. I am clearly of opinion that it was protruded from a 
vent on the spot where it now stands, and that it owes its form, 
as explained above, to the very low fluidity of its substance at 
the time of its emission. If any of the surrounding cones of 
scoriae was thrown up by the same eruption, it must most pro- 
bably be the Puy de la Fraisse. 

8, 65, 9. Put/8 de Sarcoui and des Goules. — Immediately to 
the north of Pariou rises a linear group consisting of three hills 
and having the same direction with the general chain, viz. north 
and south. The central one, Le Grand Sarcoui, consists entirely 
of domite ; the two others, Le Puy des Goules and Le Petit 
Sarcoui, are ordinary volcanic cones. 

The first of these latter hills has a shallow but wide crater at 
its summit It is remarkable only for the fragments, of gneiss 
apparently much altered by volcanic heat, of a black trachyte 
passing into a resinous state and enveloping pieces of gneiss, and 
of a variety of basalt with variolitic spots, which occur mingled 
with scoria^ puzzolana, and ashes, in its composition. This has 
been exposed by the cutting of the high road from Clermont to 
Limoges, which occupies a narrow pass between the Puy des 
Goules and that of Pariou at an absolute elevation of 3310 feet, 
and during the winter is subject to dangerous tourmentes, or snow- 
storms. 

The Little Sarcoui has a semi-crater, exactly fronting and 
embracing part of the circumference of its larger namesake. It 
gives rise to a current of lava on its eastern side, which follows 
the sweep of a granitic ridge as far as the village of Egaules, 

p 2 



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fc* MoSTS DOME AXD LDIAGXE. Chat. V. 

where h is anfounded with that of the Pot de Jume. In 
mineralogkal characters h diflers little from that of Pariou. 

60. 2* Gmd SwrtmL — Between the two last described hills, 
and in close contact with each at its base, rises the Pay de 
SareouL one of the most remarkable and perfect of die trachytic 
domes of this district. In figure it is completely a flattened and 
rather elongated hemisphere, and is aptly compared by the 
mountain shepherds to a kettle placed bottom upwards. Of 
this singular shape, which attracts die attention from a great 
distance the engraving < Plate HI.) will convey a very accurate 
idea* The trachyte which composes this hill is rather looser 
iu texture and lighter in colour than that of the Pay de Dome ; 
it has ako fewer imbedded crystals* but is essentially the 
*ame rvvk* like the Pay de Dome, Sarcom has parts of its 
suhstance impregnated with muriatic acid and stained with 
mixed and brilliant hoes of red and yeflow. Like Clierson it 
has been quarried for sarcophagi some of which still remain in 
an uutiuished state in its career and the name of the hill is sup- 
|**»nl to be dcrixcd from the purpose to which its stone was 
appliotl In these caves I thought I perceived indications of the 
structure vtf the hill in massive beds* which, as far as can be 
made out from Oh* thick vegetation and quantity of debris which 
eo\er the surface frllow the curving slope of its sides, and 
emvlop its uucleua c\«Kvntrkally. in the manner of the coats 
of «u ouk>u. It has been already remarked that the Puy 
de riiewou appears to show traces of a similar concentric 
structure 

The summit is nearly circular and quite flattened, covered 
thickh with heather* and strewed with scoriae launched pro- 
bably fltxwu «om* of the neighbouring pays* Near the foot 
of the hill oti tlve c*st a uutuber of small rocky knolls of 
truch> te |*ic<ve thn>ugh the cultivated soil* and appear to con* 



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Chap. V. PUYS NORTH OF PUY DE DOME. 69 

nect themselves with the base of this larger mass of the same 
substance. 

The very intimate union of SarcouS with the Puy des (Joules, 
together with the fact that the latter cone does not appear con- 
nected with any current of basalt, and moreover consists in great 
part of fragmentary trachyte, leads to the opinion that these two 
hills are of contemporaneous production, the latter being formed 
of the fragmentary substances projected by aeriform explosions 
accompanying or rather preceding the emission of the trachytic 
lava of Sarcoui. 

This group of volcanic hills deserves to be thoroughly studied 
by those who wish to obtain an insight into the mode of forma- 
tion of the dome-shaped masses of trachyte to be met with in 
many other volcanic districts, and which sometimes attain to the 
magnitude of the colossal Chimborazo. A rock of trachyte is 
rarely to be observed on so small a scale, so completely insulated 
from every non-volcanic rock in position, so accessible to exami- 
nation, or presenting so perfectly the figure which has been 
supposed characteristic of this formation. Those who will imagine 
the effect which would be produced by heating a very thick 
soufflet-pudding in a closely covered vessel which it completely 
fills, until its intumescence force it to exude through a crack or 
hole in the cover of the vessel, over which the matter, quickly 
congealing by exposure to the air, would cake into a bulky 
excrescence, will understand exactly the mode of formation 
which I attribute to the trachytic dome of Sarcoui, the Puy de 
Dome, and the other similar hills. Their substance, indeed, in 
its spongy and porous texture, and lightness, is really not very 
dissimilar from the sort of cake which would be the result of the 
homely culinary process I have here imagined. I beg pardon 
for so mean an illustration, but it explains my theory of the 
formation of domite better than any elaborate description. I 



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70 



MOOTS DOME AND LIMAGNE. 



Chap. V 



must add, that on revisiting these hills in the present year I 
found no reason to alter the opinion I had formed of their origin 
in 1821.* 

10. Le Creux Morel. — To the north of the Puy de Fraisse, and 
west of the group last described, is a large extent of level plain, 
covered with turf; the soil is a medley of volcanic fragments 
ejected by the surrounding cones. 

A singular depression is observed in it near the Puy dee 
Goules, evidently the result of a volcanic explosion, but differing, 
from other craters in having a conical mount of scoriae raised 
on one side only, while the margin of its remaining circumfer- 
ence is even with the plain around. It is 115 feet deep, has no 
lava-current, and was probably but a subsidiary spiracle of one 
of the neighbouring volcanic vents. A violent wind, or a slanting 



* M. le Coq, though believing that 
they were formed at the time of the 
eruption of the neighbouring cones of 
scorue and basaltic lavas, adheres still, 
I believe, to the notion that these domi- 
tie puy a are nil hollow bubbles, blown 
up by elastic vapours from a fused 
portion of a pre-e sitting bed of doniite 
or trite hylic conglomerate. Although 
1 think it perhaps possible that bub- 
bles of such a size may have been formed 
in ftome mdftilUW i MH lava masses, it 
would seem that domite, from its light, 
granular, and porous character, is the 
very last kind of luva in which they 
may be expected to occur. It is in the 
fine-grained, compact, and a I moat vitre- 
ous lavas that the largest bubble* ore 
formed. There are indeed no bubbles 
or vesicles at all to be seen in do- 
mite. It is open and loose in texture 
throughout, as cuntm -distinguished 
from the compact basaltic lavas, in the 
superficial and fiGorifurrn parts of which 
bubble* nre frequent, &jtne of the Ice- 
landic lavi-current* contain very large 



vesicular caverns, but they occur in the 
basaltic lavas, not in the trachytic ones. 
In the Mont Dore, as will be seen here- 
after, many of its trachytic lavas take 
the form of vast massive hummocks, 
their imperfect fluidity having prevented 
their flowing to any distance from the 
veut whence they were protruded* The 
domitic hills of the Mouts DAme ore in 
my opinion only masses of the same 
kind, of which the substance was when 
erupted in a still less fluid condition, 
liitumescent throughout, but having the 
elastic fluids which gave it that charac- 
ter disseminated throughout the mass: 
whence its porosity ami lightness. If it 
were considered worth while to solve 
this question by positfr* examination, 
it would not be a difficult or very ex- 
pensive operation to drive a gallery a 
few hundred feet into the side of Sar- 
cout, even to its very centre- Those 
who think a vast empty space would be 
found there would, i imagine, be then 
convinced of their error. 



Chap. V. PUTS NORTH OF PUT DE DOME. 71 

line of projection, may have caused the matters thrown up to 
fall upon the side rather than around the orifice. 

Its scoriae contain crystals of black and green augite, and of 
olivine ; the erratic blocks of basalt are unusually dense and 
hard. 

11. Puy de Chaumont. — This is a very regular and large cone, 
with a crater at the summit nearly effaced by the accumulation 
of debris. Its lava and scoriae resemble those of the Creux 
Morel, with which it was probably contemporaneous. No per- 
ceivable current ; but the basaltic rocks which here and there 
pierce through the soil of the plain on the east, are rather refer- 
able to this than any other puy. 

12. The Puy de Lantegy is scarcely more than a hillock of 
scoriae, covered by numerous fragments of domite, with a small 
crater broken down towards the west Its lava, like that of the 
other puys in the vicinity, is soon lost under the thick bed of 
volcanic ashes sprinkled over the plain, and the occasional 
cultivation which this circumstance induces. 

13. Puy de la Goutte. — This is a segment of an immense 
crater connected in situation, and doubtless in origin, with the 
extraordinary medley of rocks called Puy Chopine, which it half 
encircles. 

Fresh-looking scoriaB, and blocks of a compact basalt contain- 
ing olivine and augite, and fragments of domite, show themselves 
on its sides and interior, wherever the turf is rent away, and the 
elevation of the soil to the west seems to indicate a current to 
have taken that direction. 

14. Puy de Leironne. — This cone rises on the north of Chopine, 
that is, the opposite side from La Goutte, and by the two it is 
almost completely enclosed. Leironne has a shallow crater on 
the side towards Chopine, and seems to be composed more of 
domitic fragment**, often scorified and approaching to pumice, 



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MOXTS DOME AM) LIMAGNE- CWai>. V. 



than of angitic mrie. It ns probably coeval in origin with 
Chorine and La Goutte. 

6& The Pajf flkyyme. — His is a very remarkable vulcanic 
production, and Ins prated, and still will prove* a most perplex- 
ing subject of ^tndy to every geologist who visits Aurergne. 
D Aubuksun left h after three raits* and candidly avows that he 
had not acquired any light on hs probable mode of formation, 
nor any positive idea of its structure and composition. It may 
therefore appear presumption even to attempt to describe it ; but 
though to obtain a clear knowledge of the c omp os iti on of a hiD 
which fe evidently a confused medley of h ete rogeneous substances 
18 at the outset impassible, yet its general aspect and principal 
features may be without difficulty remarked and sketched. 

The ti^ure of the pur k irregularly conical, and its sides on 
mune points are so steep tiut vegetation is prerented from 
txmtriuj* them by the fra^nieuts which are continually detaching 
themselves and rolling to the bottom ; and hence two wide rents 
vui the east and south lay bare its upper half; the lower is con- 
cealed by the immense and duly increasing accumulations of 
debris* 

Its compo^it*^ as far as it can be observed by help of these 
Utrren facr^s* which trotu their excessive steepness and the crum- 
Wmi* nature of their materials are very difficult of access, is a 
mixed assemblage of various primary crystalline and volcanic 
recks iu diftereut stages of alteration from volcanic heat, acid 
\wpours* and atmospheric injury. 

This singular cotubtuatiotiL however, exkts but on that portion 
of the puy wluch fronts the south-west> south, south-east* and 
east, The remainder t a massive and nearly vertical bed of 
domite alvHuv The wh»\e mountain rises out of the semi-crater 
of the l\i\ do la iu*utu\ wiu»'h cl»vel\ embraces it from north- 
west to en>t. jHv«svitu: h\ the s»Hi:h. 



# 



Chap. V. PUYS NORTH OF PUY DE DOME. 



73 




LaGoutle. 2. Chopine, 



3. Cbaumont, as seen from the South. 



I spent some hours in examining the Puy Chopine at three 
different visits ; and it appeared to me that, notwithstanding 
the confusion which reigns through some of its parts, the disposi- 
tion of the principal masses is sufficiently obvious, and may give 
a clue to the aenigma of its formation. 

The lowest rock which shows itself on the face of each rent 
above the talus of debris that conceals the base of the mountain, 



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'* MOSTS 1KME AXI» UMAGKE. Chip. V. 



»* ean£knera*e of soma? and vafemir Mhes. through which 
protrude nuwerre Lk*is trf basalt, •podtfnthr is mtaL Has basah 
is either e^Zralar and sranroacnsw or atSecs* a spheroidal strata 
tope, <xaruiiis olivine and an^rte. and pole cm the dull aspect cf 
the oldtr rocks erf" tins ^ms. 

£/** tiii* rests a tabular lied <£ pxnife Die fine cf contact 
k rtra.igtit and inclined to the horiacai at an angle cf about 
15 degrees traverang the wixie £aoe cf the mountain, front 
south-west to south-east The granite far the qmce of three 
or ft«r feet from this line is flamed cf a red colour, and so 
entirely disaggregated that the fool sinks into it; it becomes 
sounder as it is more distant from thence, but hs maoacr 
present everywhere an irregular and dislocated appearance. 
Hightr op it passes on various paints — 1, into a small-grained 
granite; 2, a sienitic rock similar to coe met with near the 
Lac d' Aidat ; 3, a fine-grained hornblende slate separating into 
rhomboidal pieces ; 4, compact felspar. 

These transitions are effected suddenly, and only remarkable 
here for occurring within such narrow limits, as the same passages 
on a largo* scale present themselves on other points of the 
gneiss district The assembled primary rocks are backed to the 
north, and in part supported to the west by a rocky mass cf 
domite which constitutes all that side of the mountain. 

At the summit and wherever this junction takes place, which 
is far from being as regular and decided as that with the basalt 
below, the granitic rocks are more or less altered. The granite 
is blanched, and has lost its consistence ; the hornblende rock and 
compact felspar are also discoloured, cracked, and their fissures 
coated either by a reddish-brown ferruginous varnish, or dendrites 
of specular iron, evincing that the rock has been traversed and 
affected by volcanic exhalations. Small patches of boles and 
breccias, which are seen on a few of these points, seem merely 



Chap. V. PUYs NORTH OF PUY DE DOME. 75 

to result from the mechanical confusion, decomposition, and 
chemical changes wrought in the united rocks already men- 
tioned during their protrusion. 

It appears then that the Puy Chopine, taken in general, con- 
sists of a mass of various primary granitoidal rocks, showing 
signs of great disturbance, included (like the meat in a sandwich) 
between a bed of domite on one side and of basalt on the other ; 
and this singular aggregate rises immediately out of the crater 
of a volcanic cone of loose scoriae. 

These general features are indeed unparalleled. They leave, 
however, no room to doubt that the whole mass was raised into 
its present position by the eruption which threw up the scoriae 
that form the Puy de la Goutte. Among the clefts which are 
broken across the superficial crust of rocks, by the expansive 
force of subterranean lava, and through which all volcanic erup- 
tions take place, it must sometimes happen that two fissures 
meet or branch off at an angle, and occasion the minimum of 
resistance upon that point An eruption taking place there may 
readily be supposed to elevate a portion of the rocks forming 
this angle in a solid state, and set it on edge upon one side of 
the vent This mass would then form an obstacle to the frag- 
ments and scoriae thrown out from the vent on that side, and 
force them to accumulate into a semicircular ridge on the 
opposite side of the orifice of eruption, such as is seen in the Puy 
de la Goutte. The basalt which underlies the primary crystal- 
line rocks dates, no doubt, from this eruption, and is the out- 
cropping of the subterranean lava whence the aeriform explosions 
proceeded. With respect to the trachyte, which also in part 
underlies the granite and backs it to the north and west, it is 
difficult to determine whether it owes its formation to the same 
eruption, or existed previously in contact with the granite, and 
was raised into its present position at the same time with that 



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76 MONTS DOME AND LIMAGNE. Chap. V. 

rock. I am inclined, however, to prefer the first opinion, and 
to think that we have perhaps in this close union of primary 
crystalline rocks, trachyte, and basalt, in a mass protruded from 
the crater of a volcano, an example of the eontempcraneout 
elaboration, at a recent epoch, of the two most frequent 
varieties of volcanic rocks, trachyte and basalt, the first from 
highly feldspathic granite, the second from hornblende rock, by 
volcanic influence. If we suppose, which is not improbable, 
that the inferior and intensely heated beds of the original rock 
contained the same varieties of mineral composition as its 
superficial parts still exhibit, we may conceive how the same 
process, acting on the more feldspathose portions, would convert 
them into trachyte, which changed the more ferruginous or 
hornblendic parts into basalt ; the quartz in each being dissolved 
and partly carried off by the aqueous vapour. These different 
lavas would intumesce, and might rise almost at the same time 
through the fissures on either side of the angular and still 
solid portion which was heaved up by the violence of their 
escaping efforts; and thus this portion of primary crystalline 
rocks would remain, as it now appears, wedged in between out- 
cropping beds of trachyte on one side, and basalt on the other. 
Such a solution of the senigma offered by the phenomena of the 
Puy Chopine, corresponds certainly with the phenomena of the 
mountain, and seems to be in harmony with the laws of volcanic 
action. 

15-19. — North of the Puys de Chaumont and Chopine is a 
group of seven or eight volcanic cones scarcely separated from 
one another, and in all appearance the product of contempora- 
neous eruptions from different points of the same fissure. 

The two which rise in the centre of this group, united by a 
narrow ridge, far exceed the others in height and magnitude. 
Each has a larjr** crater at its siunmit ; that of the most northerly, 



Chap. V. PUYS NORTH OF PUY DE DOME. 77 

the Pay de Jume, is 210 feet in depth, and beautifully perfect ; 
the other is called the Puy de la Coquille. 

This system of volcanic mouths has sent forth a vast torrent 
of lava towards the east ; which, entering a branch of the valley 
of Arniat, by this opening descended to the alluvial and calca- 
reous plain below, on which it forms an extensive plateau, raised 
very considerably above the surface of the plain on either side ; 
thus presenting an admirable clue to the formation of some more 
elevated and older basaltic plateaux in the vicinity, whose con- 
nection with the granite heights, whence they probably flowed, 
having been destroyed, might, but for this object of comparison, 
have appeared problematical. 

The rivulets which drain the hills of Arniat and Laqui still 
unite in their former channel, and flow on unseen beneath the 
bed of lava, till at its extremity the whole river gushes forth 
near the villages of Sayat and St Vincent, in the most abundant 
and fertilizing springs of the country. This basalt encloses 
numerous crystals of augite and olivine, with a few of felspar 
and some plates of mica. 

20. Puy de la Nughre. — A volcanic cone, bearing traces 
of several craters : the principal one is an oblong basin, large 
and deep. It pours forth a body of lava towards the north- 
west 

Numerous smaller orifices seem to have been in action at the 
same time, and, after raising in common the north-eastern pro- 
jection of the mountain, to have furnished another mighty 
torrent of lava, which is seen to fall in a broad cascade down its 
steep sides, and, encircling a prominent knoll of granite that 
checked and divided the current, to join the former stream.* 
Together they inundate a considerable valley, and, escaping 



♦ See Plate IV. 



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78 MONTS DOME AND LIMAGNE. Chap. V. 

from it through a narrow pass, descend to the site of the town of 
Volvic, where they are either stopped or lost beneath a later 
current from the neighbouring Puy de la Banni&re. 

The rock of Nug&re has for three or four centuries past been 
quarried, and in use as the principal building-stone of the 
country, under the name of " Pierre de Volvic." It is through- 
out penetrated by numerous irregular cells lengthened in the 
direction of the current ; it contains a large proportion of felspar, 
so much so as to make it approach in character to trachyte ; in 
fact, is scarcely distinguishable from some of the trachytes of 
the Mont Dore, and bears a considerable resemblance to the 
Neidermennig mill-stone lava rock, near the Laacher See, in the 
Eiffel, as well as to some Italian lavas, especially that quarried 
near Camaldoli, of which extensive use is made in the town 
of Naples. It is of a light grey colour, and possesses the pro- 
perty of cutting with facility. The fissures occasioned in the 
mass by its retreat are few and distant Hence blocks of great 
dimensions can be extracted. I have seen some worked into 
slabs of 20 feet by 6. These fissures are lined with a profusion 
of specular iron, which is also thickly disseminated through the 
pores of the rock. 

21. Puy de LoucJiadiere. — This is, next to the Puy de Dome, 
the most striking hill of the whole chain. Completely isolated 
from the others, it rises as a majestic cone to the height of more 
than 1000 feet from the western plain, at an angle of 35°, and 
to the absolute elevation of 4000 feet 

An enormous crater, broken down towards the west, and 
measuring 486 feet in vertical depth from the highest point of 
the ridge, is scooped out of this mass. At its bottom a capping 
of basalt conceals the orifice of the volcano, and almost seems 
still to boil up from it as a spring gushes from its source : thence 
issues a vast current which, first falling abruptly down a steep 



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Chap. V. PUYS NORTH OF PUT DE DOME, 79 

declivity into the plain, encumbers a wide extent of it with hilly' 
waves of black and scorified rocks, and then, pursuing the direc- 
tion of the slope, proceeds to join the more recent Cheire of 
Come immediately above Pont Gibaud. The figure of this 
mountain originated its appellation: "La" or rather "Lou 
Chadifere " is in Auveignat " the arm-chair" It is covered with 
forests, which add considerably to the beauty, and take from the 
horror, of its aspect 

22-25. — From the base of Louchadi&re a group of five or six 
smaller volcanic hills, closely connected, extends upon a line 
towards the north. They present the vestiges of as many 
craters, which send forth currents of lava to the east, west, and 
south. The thick forests which clothe these puys render it diffi- 
cult to examine them minutely. Their lavas are uniformly 
basaltic. 

26. Puy de Pauniat. — This cone stands by itself to the north- 
east of the latter group. It has a semi-crater facing the north- 
west, and seems to have furnished its contingent to the sea of 
lava which deluges the plain in that direction, but which later 
showers of volcanic ashes, a coating of rank grass, and here and 
there the plough, have combined to smooth over and conceal. 

27. Puy de Tkiolet. — An imposing hill of an oblong figure 
partly covered with wood. Its principal crater is elliptical and 
of vast dimensions. This cone has emitted streams of lava from 
three of its sides. That which issues from below the eastern 
base was anciently quarried, and the cathedral of Clermont was 
built from it ; it was afterwards discovered that a similar stone 
was to be found nearer that town, viz. at Volvic, and these 
quarries were abandoned. 

28. Puy de Beauny. — At some distance to the north-east of 
Thiolet is a circular plain about a quarter of a mile in diameter, 
once the bottom of a piece of water called the Lake of Beauny, 



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80 MONTS DOME AND UMAGNE. Chap. V. 

which a few years back was drained. On the south it is over- 
looked and partly embraced by a volcanic cone, which exhibits a 
crater breached towards the lake-basin. On the north and east 
it is enclosed by a semicircular ridge of loose scoriae and granitic 
fragments, about 150 feet in height, on the outside of which is 
seen the granite. 

This wide crater appears to have been opened through the 
granite by some more than ordinarily violent explosions, and 
the mouth was afterwards, in all probability, closed by the 
lava of the Puy de Beauny, which, first filling the basin, issues 
from it towards the west, and unites itself to the western streams 
of the Puy de Thiolet 

The lavas of the last described seven or eight puys, hemmed 
in by ranges of granite on the north and west, and by their own 
ejections on the east, seem to have flooded the whole space thus 
enclosed with their united currents. They resemble one another 
very closely in composition ; and this similitude extends to those 
of La Nugire and Louchadiere. They are of a light colour, 
abound in felspar, are more or less cellular, highly sonorous, and 
contain few or no imbedded crystals. It is probable, indeed, that 
these puys all date from the same epoch, and were produced by 
the same crisis of subterranean effervescence. 

The connected chain of puys ends here ; but two eruptions 
have taken place north of this point upon the same meridian, 
and probably therefore on a continuation of the same primary 
fissure of eruption. 

29. — The first is the Puy de Chalar : it rises at a short dis- 
tance east of the small town of Manzat ; and three miles and a 
half in a direct line north from the Puy de Beauny. It is a 
large and sufficiently regular volcanic cone, with a vast crater 
broken down to the north-west From its interior a copious 
rurrent of very black, compact and scorified basalt takes its 



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Chap. V. PUYS NORTH OP PUY DE DOME. 81 

rise, and descends by a gentle acclivity into the valley of the 
Morge. 

30.* — Rather within a mile to the north-east of the Pay de 
Chalar is a circular lake, called LeQ-our de Tazcma, about half 
a mile in diameter, and from 30 to 40 feet deep. Its margin 
for a fourth of the circumference is flat, and little elevated above 
the valley into which the lake discharges itself. Everywhere 
else it is environed by a crescent of steep granitic rocks rising 
about 200 feet from the level of the water, and thickly sprinkled 
with small scoriae and puzzolana. These fragments are all that 
indicate the volcanic origin of this gulf-like basin, but these are 
enough. No stream of lava or even blocks of any size are per- 
ceivable. 

The encircling rocks show marks of considerable disturbance. 
They consist of two varieties of granite ; one fine-grained, and of 
the usual elements ; the other coarse, with very large crystals of 
felspar, and having the mica chiefly replaced by pinite, both 
crystallized in hexahednd prisms, and amorphous. 

This curious, and, in Auvergne, rather uncommon variety of 
crater is identical in characters with some of the largest and 
most remarkable of the volcanic maare in the Eiffel (particularly 
that of Meerfeld) ; with this only difference, that the former has 
been drilled by the volcanic explosions through granite, the 
latter through superficial strata of grauwacke slate and secondary 
sandstone.f 

The peculiar characters by which such craters are distinguished 
from the other volcanic vents we have been describing, viz. their 
great width, the total absence of all lava-current, and the ex- 



* Both of these sites of erujption are without the area of our map of the 
M onto Dome. 

f See a paper on the Rhine Volcano*, in the Edinburgh Journal of Science, 
June, 1826. 

a 



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W »F> I#*aH: AKI» UMAGKH Cm*:- T. 



r/uiiC*^ ar»r n<r eaairr j^nmnec iec. H huwror. "•* **•?«** 

HL fc'>rU21lui*aiUL Of luiHi-'T eittfElf TBimfC Xi iMfVf- fuLJaud QBt ibf 

»n?i&& of a <$uti«e?Taiieuxi i^<-«e!r^dar <£ laxa. lie at immenst 
wsj*. auc tL*-L In- TVb&.TL <£ ax in omm of ifr lanyenomv 1p 
it<j^*r f^jii'xi^c in. perimj* ft fflHiiH* or & it*w tkiaoq avthMi 
-/**• tij*r ^2j*j •KiO; uf n eieaiL i*_iiit2-*. the dkpftacec saper* 
L« 'uJ v*lj> lfcljuy Wi f_r »i#e mt« pun imv* the canity, we 
ftii'AuC *-2)**i «r,au* fco"ii resch a* iLif kind of maaswmer. 
J i*r *fit/^iu»r> v r^ruuir fdrvuiar fxrnrfc. wiiki i*. Amrt a i '■<» erf 
t.- mi-*L ♦•ntV'ft. d^isi^.tti^&btfT^jT je\ir«> thai iiie exjtkiaom of one 
<*r lu'^^r *:\&t*u ( : buboi** v^ #-» ci-.^sn^d iii »i**-ir pr\«rortkm. Had 
tij*ff *• U**ju u Vrix&i&i&d eerie* i*f sq?L exj«i t&an& as in tbe> 
j>haj*r tf \<n i iiiA*' *ru]*i«.*L these wocid necessarily have 
up * \aayw 'jijuajtitr of w*Mvt and other frapneataxy 
4uvi l*tru&A the u*ual circular rid^e or cane round tkf 
*l*rr^a* in tl*r«*f iiuftanne* such ejections are almost wholly 
* tutting, 

Tim (i**w de Tazana is not quite a solitary instance of this 
j/luu* f/f volcanic development in the chain of pay*. Hie Lac 
d<: ^Uft^^uy t already described, seems to owe its origin to some 
timiUr explo*ion on a minor scale ; and we shall hare occasion 
Iwn'JtfUfr to remark its repetition in mote than one locality of 
tin* MfHit flora. 

Eastern Line op Puts. 

Tlir**** otlu-r volcanic cones occur near the eastern limit of the 
graiijh' pliiN-rtii, at some little distance from the meridian on 
which ri*« thl <?hain of Puys hitherto described. 

ill. |W <U la Bannttre. — An eruption has, in this instance, 
takm plivv i it i the summit of a granitic eminence overlooking 
tin* vuliuy-plain of the Limagne, and a vast current of lava has 




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Chap. V. EASTERN LINE OF PUYS. 83 

taken that direction, rushing tumultuously down the side of the 
mountain, and spreading over a large level surface below. 

No regular cone or crater is to be observed ; but prodigious 
heaps of scoriae, volcanic bombs, lava-blocks, and fragments of 
granite, surround the spot whence the current issued. The shelv- 
ing sides of the hill might, indeed, be expected to prevent the 
accumulation of these incoherent substances in the figure they 
usually affect The town of Volvic is -built upon the basalt of 
La Banniere, which crosses and apparently covers that of La 
Nugere. Copious springs gush from below it both at St Genest 
and Marsat It is of a black colour, compact, contains numerous 
crystals of augite, and fewer of olivine and felspar ; and in all its 
characters contrasts with the lava of Nug&re, bearing the strongest 
similitude to theHbasait of some of the most ancient plateaux. 

32. Put/ de Channat. — This cone is partly covered with wood, 
which perhaps conceals the vestiges of its crater, nowhere else 
observable. Its scoriae frequently envelop fragments of granite, 
and large knots of olivine and hornblende. The latter are rounded 
and amorphous, appearing as if they had suffered bouldering, or 
external friction. They are of a deep black, and exhibit a laminar 
structure only on fracture ; the faces of the laminae are highly 
lustrous. Crystals of the same mineral, with grains of compact 
felspar of a bluish-white colour, are to be found in the lava of 
which this puy has furnished two currents. One descends directly 
to the east, and is lost immediately under a cultivated soil ; the 
other directs itself at first to the S.W., but is conducted by the 
inclination of the ground into the bed of a small stream, which 
it continues to occupy, making the circuit of a granitic hill covered 
by a fragment of a more ancient basaltic current, and disap- 
pearing towards the east below the village of l'Etang. 

33. Gravmeire. — This volcanic cone has been more frequently 
visited and described than any other, from its immediate vicinity 



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84 MONTS DOME AND UMAGXE. Chaf. V. 

to Clermont The eruption to which it owes its origin burst 
through a bed of basalt, which covered the eastern slope of a long 
crescent-shaped granitic eminence, called the Puy de Charade, 
one of the highest points of the plateau. 

The scoriae, lapilli, and puzzolana, of which the cone of Grave- 
neire consists, have an exceedingly fresh appearance : they are 
red, reddish-brown, and black, and are often met with in the form 
of bombs, tear-drops, and long ropy sticks. The puzzolana is in 
great request as an ingredient in the mortar of all the neigh- 
bouring edifices: it is called "gravier noir" by the natives, and 
hence the mountain's name. 

No crater is visible; probably it was destroyed during the 
emission of the last current of lava, which seems to have descended 
from the very summit of the present cone towards the north into 
the valley of Boyat, stretching thence into the plain as far as 
Mont-joly and Les Roches.* 

Two other streams are seen to proceed from the midst of scoriae 
on the top or side of Graveneire, towards the east and south. The 
former is diverted from its course by a calcareous eminence, on 
which rises the Puy de Montaudoux, a conical rock of older 
basalt, and both unite to deluge an extensive surface of the 
plain below. 

The interior of the bed of basalt in the valley of Boyat is dis- 
closed on each side of the vast excavation already effected through 
it by the rivulet It measures 65 feet in thickness, and is 
divided by vertical fissures into imperfect prisms, or polyhedral 



* See Plate I. Those geologists who, thick, at angles exceeding 40° on the 

forthe purpose of supporting the strange upper part of the cone. And yet the 

theory of "elevation craters/' affect to bulk of this lava was so liquid as to 

dnny that a stream of lava can harden flow to the distance of 4 or 5 miles, 

on the slope of a hill at an angle above 4° and spread in a wide sheet over the 

or 5 \ should examine those of Grave- plain beneath, 
neire, which rest in beds at least 10 feet 




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Chap. V. 



EASTERN LINE OF PUYS. 



85 



blocks, strongly resembling in general appearance the forms 
assumed by many granites. These blocks are sometimes replaced 
by globular concretionary masses, with a concentric lamination, 
of which the woodcut annexed affords an example taken from a 




6. Lava-Rock of Grarenelre, showing an imperfect Prismatic and Spheroidal Structure. 

rock near Roy at From some of the fissures of this lava-rock 
spring the copious sources which by means of an aqueduct 
supply Clermont with an abundance of the clearest water. 

Within the gardens of Mont-joly, at the extremity of the 
northern current, is a small cavern rivalling the Grotta del Cane 
in its phenomena. A constant emanation of carbonic acid gas 
takes place from its sides and bottom ; its mephitic qualities have 
been ascertained by repeated experiments ; and in the village 
of Royat, at the northern verge of the lava-bed, very copious 
hot springs have lately been discovered, and applied to the purpose 
of an establishment of baths, built on the site of one formed there 
by the Romans, as attested by considerable remains. 



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Sfi M0NT8 DOME AND LIMAGNE. Chap. V. 

The basalt of Graveneire, taken from the inner parts of the 
current, is compact, dense, of a deep slate colour or greyish-Mack, 
and contains crystals of angite, with a few of olivine and glassy 
felspar. The superficial parts are more or less cellular and sco- 
rified. Its texture is sometimes as highly crystalline as any of 
the oldest basalts. 

From its proximity to the populous town of Clermont, the 
surface of the Cheire of Graveneire has been forced into cultivation 
by the most assiduous industry. The process is to break up all 
the projecting masses of basalt by blasting ; and from their frag- 
ments and scoriae, aided by dressings, a soil has been created and 
clothed with vineyards, which almost rivals the well-known fer- 
tility of the sides of ^Etna and Vesuvius, where the same method 
has been constantly pursued. 

PlJYS FACING THE PlJY DE D6ME. 

34. Pay de (Jol&re. —About 200 yards from the eastern base 
of the Puy de Dome rises a diminutive cone of this name, which, 
seemingly from its insignificance, has as yet escaped the notice 
of every writer on the Monts Dome. It has, however, to all 
appearance, sent forth a considerable stream of lava, which, after 
spreading to some extent over the plateau, encountered a hill of 
granite above Font de FArbre : a division took place, and one 
portion joined to the left the current of Pariou at Les Cheix, 
while the other threaded the narrow valley of Fontanat, and 
accompanied its rivulet to Royat, where it either terminated or 
has been since covered by the stream descending from Graveneire. 

The basalt of the current of the Puy de Coliire is dark- 
coloured, dense, brittle, and remarkable for being generally 
replete with numerous nearly spherical cells. Its crystalline 
texture is evident to the naked eye, and exhibits a multiplicity of 



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Chap. V. PUYS PACING AND SOUTH OP PUY DE DOME. 87 

minute crystals of glassy felspar; those of augite are not so 
conspicuous, but some crystals of this mineral and of olivine are 
scattered through the mass. 

35. A short distance south of this is a still smaller cone, known 
to the shepherds by the name of Chuquet * Geneto, probably from 
the broom (genet) which grows upon it. It has produced no lava, 
and was perhaps thrown up by some casual explosions finding 
a vent in this direction during the more violent eruption of the 
neighbouring puys. Its scoriae, which are very fresh, contain 
many imbedded fragments of granite at different stages of altera- 
tion by heat, and nodules of hornblende similar to those of the 
Puy de Channat 

36, 37. Puys du Petit et Grand Sauti. — Two small cones west 
of the Puy de D6me, in which it is difficult to discover traces 
either of craters or lava, from the quantity of turf which clothes 
and surrounds them. 

Westward of the river Sioule three or four other volcanic cones 
rise from the primary platform, viz. the Puys de Banson, de la 
Vial, and de Neufont. Not having visited these, I can give no 
details on their phenomena.! 

Chain of Pdys south of the Puy de Dome. 

38. Puy de Gromcmmx. — An eruption has in this instance, as 
was noticed before, forced its way through a bed of domite, the 
prolongation of the base of the Puy de Dome. A vast semicrater 
facing the N.W. discloses this rock in situ, and it projects also on 
other points of the puy. 



* The term "Chuquet" acta as the MM. Bouillet and Lecoq in their * Yum, 

diminutive of Puy, and is applied by &c.,duDepartenient du Puy de Dome,' 

the Auvergnat* to any small knoll or p. 219, but I have met with no other 

cluster of rocks. account of them. 

f They are mentioned cursorily by 



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88 MONTS DOME AND LIMAGNE. Chap. V. 

From the midst of this crater rises — 

39. The Puy de Besace. — A double cone covered with tur£ 
and, like the last and other neighbouring puys, presenting 
numerous fragments of domite mingled with its scoriae and 
lapilli. It perhaps contributed to the basaltic lava-currents 
which have deluged the western slope of the granitic plateau. 

40. Puy de Salomon. — A wide crescent, half encircling a 
crater which has pushed forth a large stream of lava to the west 
Erratic fragments occur on this hill of a compact basalt, of light 
grey colour, and granitoidal texture so coarse as to exhibit its 
imperfect crystals to the naked eye. Three-fourths of these are 
of glassy felspar, the remainder of green augite, with a few of 
bright yellow olivine. The cellular cavities of this lava are 
lined with more perfect crystals of the same substances. 

41. Puy de Montchid. — Four volcanic mouths combined to 
raise this mountain. Its northern crater is of vast diameter, 
and 340 feet in depth. That to the south-west appears to 
have given rise to the current of lava which descends below 
Alagnal 

The great proportion of domitic fragments which enter into 
the composition of this and the neighbouring hills, and which are 
scattered over the plain on each side, lead to the presumption 
that a considerable bed of this rock once existed on their line, 
and has been subsequently broken through, and launched into 
the air by their explosions. The road cut along the base of the 
Puy de Montchte has uncovered many charred trunks of trees 
buried in the dejections of the volcano. 

42. Puy de Barme. — This volcanic hill stands by itself, a 
little to the west of the chain. It has three distinct craters ; 
two at its summit which are perfect* and a third broken down 
towards the south-west From hence issued an immense stream 
of lava, which widely flooded the western slope of the plateau, 



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Chap. V. PUTS SOUTH OP PUT DE DOME. 89 

and reached the Sioule on the site of Pont dee Eaux. Usurping 
the channel of this river, it flowed on towards the north, and 
stopped beyond the village of Olby. 

M. de Montlosier, who so well describes the changes wrought 
in the direction of the Sioule by the lava of Come, seems not to 
have observed this third invasion, which has forced its waters to 
wear themselves a new bed through the hill forming their 
western bank, and consisting of a clayey alluvial tuff, a ramifi- 
cation of the Mont Dore. 

43. Puy de Laschamp. — This hill when viewed from a distance 
has nothing of a volcanic appearance. It is a long-backed ridge 
formed by the united ejections of three or four craters, which 
have considerably defaced one another. Its highest summit, 
seemingly the result of the last eruption, is nearly 1000 feet 
above the village of Laschamp in the plain immediately 
below. 

On the north exists the greater part of a large oblong crater ; 
and a current of lava, springing from its base, turns to the east, 
and covers a considerable space enclosed between the Puy and 
the opposite heights of granite. Overflowing here, one portion 
of the current takes to the left, skirts the base of the Puy de , 
Dome, and descends to Enval, where it joins that which derives 
from the Puy de Coliere already noticed ; the other enters the 
little valley of Beaune, but disappears before it arrives at Font- 
fredde, beneath the meadows of the low ground it occupies. 
The basalt of this current is cellular and coarsely crystalline, of 
a light grey colour, verji similar to that of the Puy de Salomon 
above described, has a large dose of felspar in the composition of 
its base, and imbedded crystals of this mineral and of olivine. 
A separation into rude columns is observable on some points. 
Another semi-crater to the left has also emitted a stream of lava, 
which, after joining those of the Puys Lamoreno and Montchar, 



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1 



SO MOOTS DOME AND LIMAGNE. Cn*F. T. 

two iK^vttirtciw of Laachamp closely united to it, spre a ds oicr 
a |Murt of like western slope. 

IV Uk* $mtfth of the Put de Laschamp rises an irvegwkriy 
ciiYUAar *x^«a of volcanic cones, the produce of many repeated 
cntpttotfct *iuun a small space* which in all probability succeeded 
\*h> am titer w ckwhr. or raged at the same epoch. TUt is 
ri*o utv^t m«ow«UDur ]Mtion of the whole range to every observer. 
whether ^\Hvy*4 or aoC The extraordinary character of the 
>tew fivm an* vw of these pays impresses it for ever on the 
tt^rnvry l^wrv fc no spot amongst the Phlegraean fields of 
1*&N *r S*tN wiuv*h di<pi*y$ in greater perfection the peculiar 
h*;h«y* of * w^ttttry desolated by volcanic phenomena. 

b » isw tuat the <x«rk thrown up around are partially 
%wsk\i *nd tk <yno«d wven?d with herbage ; but the sides of 
<**** asv ^ - **ix\L and the interior of their broken craters, 
h^nv vV*o< **d a>*t>\l as well as the rocky floods of lava 
w>A %\.v\ vv> K*w V«ded the plain, have a freshness of 
xv^sv*v >«* i ** i^" jwh*'** of in* akme could have preserved so 
W,<, vsi o%Vr * srXv.r,*; pirt«i*of the operations of this element 

VV * s vi >v*v *" k > ^ wwnte itself commencing on the east is, 
4 V T- *\t i V ^w^.— It has a small crater on the 
\«t»"M V A*sl *v v s* *s'vr**v remarkable* 

4\ V* ;\« X . * or -i U JH.-ji*. which occurs next, has a 
U- w ^ k «* ^ - AV *v\ \ **\ p t*,nnir the east ; from its interior 
|m\wsm v^s\ >* rs«: Vr ww of tSo whiS bolky lava-currents of the 
Mo*tx IVsv V*Vr w.^ a mide#pace above Fontfredde 
wuN a ^>a ^ * V;v.va: v v *a\*. th» «pper current stops there, 
* m a V*Mt N\i o* * \U*^ Uva Aows itself from beneath, 
„^io\> iV \V.\> of Vv.v *^1 \w«|Aes the winding bed of 

• >w r *w v. 



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Chap. V. AMPHITHEATRE OP TOLOANOS. 91 

its rivulet « for as Jtdliat, where it terminates a course of ten 
miles, performed with a fall of 1700 feet Copious springs gush 
out at Fontfredde from beneath the upper bed of lava. 

The scoriae of the Puy Noir are exceeding dark coloured, 
and justify its appellation. The lower lava contains frequent 
crystals of augite and olivine ; and where the current has been 
obstructed by rocks of granite narrowing the gorge through 
which it flowed, an imperfect columnar configuration may be 
observed. 

46. Puy de Las Solas or de la Chravcuse. — This cone encloses 
a widely breached crater. Its steep walls of black and crumbling 
scoriae half surround an abyss, which almost seems still to vomit 
forth an impetuous torrent of lava. This immediately joins 
that of the 

47. Puy de la VaeAe, — a ruined crater, the exact counterpart 
of the last puy, to which it is united by the base. 

The whole appearance of these two remarkable hills forcibly 
demonstrate that the showers of scoriae which created them were 
thrown up previously to the emission of any lava ; and that this 
substance, afterwards rising in a state of liquefaction through the 
chimney of the cone, filled the funnel-shaped cavity of the crater, 
broke down by its weight the weakest side, and rushed forth to 
deluge the surrounding soil. In the interior of the upper part of 
the remaining circumference of the Puy de la Vache, the point 
to which the lava rose in the crater is still marked by a projecting 
ridge of light scoriaceous matter of a reddish yellow colour, rich 
in specular iron, and considerably decomposed by sulphureous 
vapours ; apparently part of the frothy scum which formed upon 
the surface of the ebullient lava, and adhered to the side of the 
vase at the moment of its being emptied. 

A stopper of basalt still chokes up the orifice below, and 
connects itself with a vast current, which, being swelled by the 



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7_r^ ^ ~— ^ " " — "~ i T--1- ^- .*-** r *2*» mtfceni 



13*— ~ ^moco. a «kkh the 
«£kt » ^<««d by directly 
rv m.aeL »a* rendered more 
r :~ ti* «;-au> regular eo- 
ra^rire of th* day, and the 
wtj^i t*i hardened it. 



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Chap. V. PUYS SOUTH OP PUY DE DOME. 93 

puys, as we have seen, are almost wholly composed of felspar, 
and consequently present much fewer asperities.* 

Some of the scoriae of the Puy de la Vache appear to have 
suffered an alteration from the action of acid or sulphureous 
vapours ; they are found of various tints of white, yellow, blue, 
red, and black ; they abound in specular iron, which is also found 
to have insinuated itself by sublimation into the fissures of 
compacter lava-blocks, forming within them the most delicate 
dendritic ramifications. 

48. Puy de Vichatel. — This cone has a regular crater sloping 
towards the north-east Its lava mingles with the currents of 
La Vache and Las Solas. 

49. Montchal. — A regular cone with a semi-crater fronting the 
north ; it is partly wooded. Its lava probably is concealed by 
that of 

50. Montgy. — This puy has sent forth a considerable stream 
of lava from a crater broken down towards the south-east, exactly 
in the direction of Montchal ; which appears to have divided the 
stream into two branches. They are lost immediately under the 
ashes and other loose matters with which the plain around has 
been strewed by subsequent explosions, and the vegetable soil to 
which their decomposition has given rise. 

51. Pourcharet. — A large and imposing cone, the most west- 
erly of the group. Its sides are steep ; and on the summit is a 
wide but shallow crater. Lava has issued from its north-western 
base, and followed the slope of the plateau to some distance in 
that direction. 

52. MoniUlet. — A crescent-shaped ridge of little elevation; 
from the semi-crater it encloses proceeds a current of lava, which 
turning to the right joins that of Pourcharet. 



* See p. 65 above. 



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94 MOXTS DOME AND LDfAGNE. Chap. V, 

53. Mmtjughat* — This pay stands by itself, and is one of the 
most regular of the chain. The crater is deep and large. ItB 
lava appears to have joined that of Montillet 

54. Puy de la Taupe — bo named from the resemblance which 
it bears, in common with many of the rest, to the labours of 
some giant mole. It has a crater breached towards the west, 
and its lava covers a considerable surface on that side. The 
basalt of this current is remarkable for containing even more 
crystals of augite than that of the neighbouring puys. It is 
exceedingly dark-coloured and compact 

55. 56. Puy* de Brouemm and de Combcgnme. — These cones, 
closely united, have craters open to the south-east, and furnish a 
current which turns to the east and reaches that of La Taupe. 

57, 58. Puy* de la Rodde and de Chalard. — The former is a 
large hill apparently produced by more than one volcanic mouth. 
It has a semi-crater feeing the south, and gives birth to a current 
of lava which spreads to the right and left, reaching the village 
of Aidat, at one extremity of its lake. 

The scoriae of the Puy de la Bodde are remarkably rich in 
tals of augite of the most perfect regularity, and the basalt 
of its current equally abounds in crystals of this mineral and of 
olivine. 

The Puy de Chalard appears to have been thrown up by a 
lateral aperture, immediately after the eruption which created 
the Puy de la Rodde. 

59. Puy de CharmonL — This cone has a large and deep crater 
broken down towards the south-east ; from the bottom issued a 
rurrent of dark-coloured lava, but was prevented by a ridge of 
granite from reaching the lake of Aidat 

00. Puy de TInfau or TEnfer. — A low but large crescent, the 

remaining walls of a vast crater, whose site is now occupied by a 

i r alar bog called La Narse d'Espinasse, from the nearest village. 






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Chap. V. ROOKS FROM EARLIER ERUPTIONS. 95 

The plain to the east and south is formed of ancient beds of 
basalt, and a violently explosive eruption has here evidently 
made its way through the continuation of these : their sections 
may be observed round the interior of the crater. A current of 
lava has been vomited by this opening towards the east 

61. Puy de Montenard. — The most southerly of the chain of 
puys belonging to the Monte Dome appearing in our map. 
Its figure is irregular, the result of two neighbouring craters. 
One of them is open to the south-east, and a copious stream of 
lava has issued from it> covering a wide space on the south and 
east, and reaching to the bed of the river at Monne. But the cul- 
tivation of the plain from which this puy rises, and the quantity 
of more ancient lavas which have flowed from the Mont Dore in 
its direction, renders it difficult to ascertain the boundaries of the 
recent currents with due precision. Although the continuous 
chain of puys ends here, another very recent cone and lava cur- 
rent, called Tartaret, occurs on the continuation of the same 
meridian at the distance of about three miles. But as that point 
is within the circuit of the system of Mont Dore, its description 
is postponed for the present 

Volcanic Bocks the Product op earlier Eruptions. 

The eruptions that produced the chain of puys just described, 
though far from being all contemporaneous, evidently belong to 
a period during which the volcanic energy raged with peculiar 
fury along the line they occupy ; a fury by which it appears to 
have been completely exhausted, and which may be the cause of 
its subsequent inertness.* 



* Eruptions which occurred within produced a chain of cones, some thirty 
the six years from 1730 to 1736 in the in number, and a sea of lava, which 
island of LAnoerote, one of the Canaries, deluged a vast surface. These craters 



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96 MOOTS DOMH AND UMA6NE. Chat. V. 



But a close observation cogri D c mgh demonstrates that pre- 
vious to this era of intense a c tivi t y erupt i on s were cfitrnnally 
taking place within the same woe, without any quiescent interval 
of sufficient duration to enable as to mad: oat a decided line of 
separation between the recent and the ancient volcanic remains 
of the class that now occupies our attention. 

For the convenience of description* however, I have thought 
it necessary to draw an arbitrary division between those already 
described as unquestionably wry rant; and those to which we 
now proceeds which are of earUer production* 

The twiner have been mentioned in die order of their geo- 
graphical occurrence ; the character and position of the latter 
will be best understood if we consider diem in the inverse of 
what appears to be the chronological order of their formation, 
ivnunenctng with die products of die eruptions which seem to 
have tnuuediately preceded those already described in the chain 
of puvs* 

They const* of currents of basalt* of whidh the originating 
cone* and craters either no longer exist, or are partly obliterated ; 
which are wore or less denuded of their accompanying accrue 
iv scorified surtaces; affected by decomposition; often divided 
aud parcelled out into fcolatcd plateaux or peaks; or finally, 
ahtch overlook valleys or ravines of considerable depth evidently 
excavated siuee their formation* 

t»7. The l\iy Kou^e near Chalueet* on die left bank of the 
8iouto % about two miles below Pout GibaucL is one of die first 
connect^ huks Ivtweeu die recent and more ancient eruptions, 
pu-^essiu^: tlie priucijial characteristics of either class* It has 



vt*"ft*l xikv«wh^v>> wouk i 'uw sttwtcih fully jy Von Btodk aod Sir C Lywll 

*H£**vm*\ 'ttv **.«*•& »t av N.«hL *n» K*»nctpui*. !<\V» jk *AT t aad promt 

ovmi.»* tho iitw<:\« •>* a <rt*t *u »tcr» » "wuwrka^iw rwraiZfttl to tb« ckb of 

tniKOtt to*uiv« TV? •** %K*ct*N*t mc«H wioar vNMi of AvrcKgw. 



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Chap V. ROCKS PROM EARLIER ERUPTIONS. 97 

burst forth from gneiss which environs it on all sides ; and a 
considerable cone, composed throughout of lapilli, puzzolana, 
volcanic bombs, and scoriae of every fantastic form, still marks 
the site of its orifice. At the northern base of this hill facing 
the Sioule, commences an enormous current of basalt, which 
evidently once flowed into and entirely choked the valley, 
extending more than two miles down the stream. 

The river has subsequently worn itself a new channel between 
this accumulation of basalt and its northern bank ; and the vast 
dimensions of this excavation eaten out of solid primary strata 
to the depth, in parts, of 50 feet below the level of its former 
bed, upon which the basalt is seen to rest, evince the long con- 
tinuance of the erosive action, as well as its irresistible power. 
This amount of excavation can only be attributed to the river 
which still flows there, because the undisturbed and perfect state 
of the cone of loose scoriae demonstrates that no denuding wave, 
deluge, or extraordinary body of water has passed over this spot 
since the eruption. 

The massive cliffs of basalt that beetle over the gorge thus 
formed have a striking aspect The thickness of the bed 
averages, perhaps, 150 feet ; its upper surface is level, but covered 
with scorified protuberances, and, where it has not been forcibly 
brought into culture, as ragged as any Cheire of the Monts Dome. 
These portions of cellular and shaggy basalt are, however, 
merely superficial ; the interior and great mass of the current is 
compact, and remarkably divided into very small prisms grouped 
together in curved and radiated bundles. Beneath it is a bed 
of sand, gravel, and bouldered stones 3 feet thick, evidently the 
ancient bed of the river at the time of its invasion by the lava- 
stream, but now from 20 to 50 feet above the present channel, 
which the Sioule has since cut for itself through the gneiss 
beneath. In the latter rock several galleries have been opened 



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98 M0NT8 DOME AND LTMAQNE. Chat. V. 

below the lava, for the extraction of lead ore, which ocean in 
veins of the gneiss. Some of these were worked at a very early 
period, probably by the Romans ; much ore is still extracted 
by a company recently formed. 

On some points of this current the prismatic is replaced by a 
spheroidal concretionary structure on a small scale, the basalt 
separating at a touch into minute angular globules, rarely 
exceeding the size of a pea, the " pieces s^pardes grenues " of the 
French geologists. There is not the least probability of this 
structure having been produced' or even disclosed here by 
decomposition ; on the contrary, large horizontal masses of this 
nature alternate with others that are prismatic on a propor- 
tionately small ' scale ; the latter modification appearing to 
pass into the former by the sole diminution of the axes of 
condensation. Where the basalt is seen in immediate contact 
with the supporting gneiss, this last rock has suffered a partial 
disintegration, and is stained of a bright red colour to the depth 
of a few inches. 

In its mineralogical characters the basalt of Chalucet resembles 
some of the most ancient varieties ; it is compact, heavy, of a 
dull aspect, a dark colour, and without any apparent imbedded 
crystals. It frequently envelops fragments of granite and 
mica-slate, considerably altered; and I have found amongst 
its scoriae blocks of a porphyry similar to that of Chateix near 
Clermont 

68. Put/ de Charade. — A considerable granitic eminence on 
the western edge of the plateau. Its summit is covered by a 
massive bed of basalt, prolonging itself with a rapid slope towards 
the east, till it is interrupted and concealed by the more recent 
volcanic cone of Graveneire, which appears to have exploded 
from beneath it 

On the opposite side of this hill, and at a lower elevation, the 



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Chap. V. ROCKS FROM EARLIER ERUPTIONS. 99 

same bed of basalt reappears, and is easily recognised by its 
peculiar characters: it immediately encounters the still more 
ancient basaltic rock called the Puy de Montaudou,* and is sepa- 
rated by it into two branches, which reunite below, and follow 
the slope of the hill as far as the level of the plain. 

A few sconce are observable on the summit of the Puy de 
Charade, sufficing to mark it as the site of an eruption, but no- 
thing resembling a cone or crater. The basalt contains very 
large crystals of augite and nodules of olivine, has a dull and 
leaden aspect, is considerably decomposed, and assumes a fre- 
quent division into spheroids of a foot or more in diameter, 
which desquamate in concentric laminae ; yet, notwithstanding 
these .numerous characters of great antiquity, its disposition in 
the form of a current of lava descending from the granitic 
heights into the main valley below is so evident, that M. Ra- 
mond felt obliged to rank Charade in the class of modern 
volcanos.f 

The granitic sides of the mountain must, however, have wasted 
prodigiously, and the deep and wide ravines on either side 
been altogether formed, since the deposition of this lava-bed, 
which now hangs over them in a rocky ledge ; while their 
sloping sides show them to have been excavated gradually by 
running water. Moreover, the main valley into which the lava 



* See Plate I. The basalt of the Puy strata of which are much confused and 

de Montaudou is very compact, fine- tilted up at the line of junction. I pre- 

grained, hard, and black. It occasionally sume it to be a dyke of basalt protruded 

contains small granular crystals of fel- on the spot from beneath the tertiary 

spar resembling those of Egyptian por- strata close to their junction with the 

phyry, and grains of peridot. The puy granite. It is remarkable that this 

is a mere conical rock, of which it is protuberance has evidently divaricated 

difficult to ascertain the structure, from both the old lava-current of Charade 

the vegetation which clothes it. Some and the more recent one of Graveneire 

rude prisms show themselves at the in their descent from the western 

summit; and to the west it may be seen heights behind it. 

to rest on the freshwater limestone, the f Nivellement des Plaines, 1815, 

H 2 



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100 MONTS DOME AND L1MAGNE. Chap. V. 

of Charade descended, almost to the level of the present plain, 
must have existed previous to the excavation of these minor 
valleys, and consequently it is impracticable to assume the 
formation of the valleys of this district in general as constituting 
an epoch or as marking any fixed period. Further proofs of 
this fact are to be met with on many points, as well of Auvergne 
as of the Velay and Vivarais. Their evidence will be dis- 
cussed as we go on. 

69. Puy de la Roulade. — A bed of basalt remarkable for itB 
uniform separation into very complete spheroids, surmounting a 
small calcareous hill a few yards above the rivulet of Boiseghoux, 
and nearly on a level with the plateau formed by the more 
recent lava of Graveneire on the opposite bank. This might be 
supposed part of a secondary current from Charade, but that in 
mineralogieal characters it differs materially from the basalt of 
that mountain. Its little elevation above the plain demonstrates 
the comparatively recent date of its formation. 

70, Plateau of Chattau-gay. — An isolated bed of basalt 
covering a wide extent of the calcareous freshwater formation. 
Towards the Limagne it rises from the plain to an average 
height of 450 feet; but on the south-west the plateau formed 
by the lava of Jumes (16) equals it in elevation, and imitates 
it entirely in disposition and structure. The productive cause of 
the one is so evidently that of the other, that it is impossible to 
escape the conviction of their identity of origin. It is equally 
clear that the more complete insulation and greater elevation 
of the former above the plain is owing only to its having been 
longer exposed to meteoric erosion. 

This current appears not to have had its source on the 
granite, but at a short distance from the limit of the two forma- 
tions ; and the she of its crater is still attested by the tumefied 
and cellular nature of the basalt of the north-west extremity, 



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Chap. V. ROCKS FROM EARLIER ERUPTIONS. 101 

by the scorified masses, and, above all, by the numerous lava- 
drops or volcanic bombs (an infallible sign of an eruptive vent), 
which abound there. This is also the most elevated point of the 
plateau, and from hence it slopes gradually towards the south 
and east It is generally modified into rude columnar prisms, 
which in parts evince by decomposition a spheroidal concre- 
tionary structure, and in others divide either into massive tables 
or slaty laminae, between which arragonite is often found crys- 
tallized 

71. Plateau of La Serve.* — This remarkable sheet of basalt 
owes its chief interest to the circumstance of its remaining almost 
entire, and exhibiting in consequence that peculiar disposition 
which would be assumed by a stream of fluid matter descending 
an inclined plane, and occupying the lowest levels, although it 
now forms the capping of a high hill-range. 

That it flowed as a current of lava is moreover attested by the 
scoriae upon which the bed of basalt rests, by the scorified and 
cavernous masses which still remain on its surface, but which 
adhere to and form part of the compact and solid rock below, 
and by the site of the vent which produced it being still cognis- 
able on its highest extremity. 

On the other hand, this basaltic bed has all the characteristic 
features of the more isolated and hitherto contested plateaux. t 



* See Plate I. and in totally different circumstances 

f It must be remembered that at the from those characterising a recent vol- 

date of my examination of this country canic sub-aerial eruption. I have re* 

(1821-5) the contest was still raging tamed in this edition some passages like 

between Neptunians and Vulcanists as that above, in which these doctrines, 

to the igneous or aqueous origin of the now all but exploded, are controverted, 

fleet* traps, and that even those who because even yet the fallacy, I believe, 

admitted their igneous origin still in- is scarcely extinct that horizontal and 

sisted that all the flat sheets of basalt so extensive sheets of basalt are almost 

frequently found capping high plateau- necessarily of subaqueous origin, 
shaped hills were formed under the sea, 



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102 



MONTS DOltE AND LIMAGNE. 



Chap. V. 



Its elevation varies from 850 to 400 feet above the water- 
channels of the valleys on either side : and a branch of it, cut off 
and separated from the main current by a subsequent excava- 
tion, has assumed that conical form so general amongst basaltic 
remains, and to which the waste of ages tends to reduce all, and 
crowned by a ruined fortress, called Monfeedon, imitates exactly 
the Stolpens and Eoenigsteins of other basaltic districts.* 

The current of La Serre originated in the granite, and the 
most considerable moiety of its extent rests upon that rock, the 
remainder on the freshwater limestone. Its western summit, 
called the " T6te de la Serre," or Puy de Nadailhat, measures 
3461 feet from the sea-level. It terminates to the east in a 
projecting tongue of hill, the point of which has suffered a 
partial separation from the rest On this point stands the village 
of Le Crest, at an absolute elevation of 2044 feet, giving a 
difference of level between the two extremities of 1417 feet, 
with a direct distance of rather more than six miles and a 



* This process has been repeated on 
numberless points of Auvergne, where 
almost at every step we meet with isolated 
and conical peaks, each consisting of an 
immense group of basaltic columns con* 
verging towards the summit. All of 
these were seized on in turn for the 
sites of fortresses, in those times of 
anarchy when an inaccessible position 
was the necessary condition of security 
to person or property. Such were the 
castles of Mont-rognon, Montredon, 
Mont-rodeix, Mont-celets, Vodable, Us- 
son, Nonnette, Buron, Mozun, Murol, 
Vandeix, Bonnevie, Mercosur, Ibois, 
Mercurol, &c. Ac. From the number 
of these strongholds and the almost 
impregnable nature of the greater part, 
the feudal tyrants of Auvergne out- 
lasted those of the rest of France; and 
it was not until the ministry of Richelieu, 



and the vigorous reign of Louis XIV., 
that a final check was given to their 
career of violence and rapine. Many of 
them were judicially condemned and 
executed at Clermont by a special court 
held there and called "Les Grands 
Joure," a fate they well merited. 
Orders were then issued for the de- 
molition of all the chateaux-forts of 
Auvergne, and little now remains of 
them but the foundations, and some 
fragments of their massive walls, which 
were generally constructed of basal tic 
prisms taken from the peak itself, and 
laid horizontally. Puxsolana was mixed 
with the mortar used in these con- 
structions; and without the binding 
quality communicated by this ingre- 
dient, probably no cement would have 
taken effect on the smooth and iron 
surfaces of the prisms. 



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Chap. V. ROCKS FBOM EARLIER •ERUPTIONS. 103 

quarter. The inclination therefore of this bed of basalt corre- 
sponds almost completely with that of the two very recent lava- 
currents which have flowed down and now occupy the bottoms of 
the valleys on either side of it ; the one proceeding frpm the 
Puy Noir, the other from the group of cones about the Lake 
Aidat :* moreover, the distance to which it reaches is about the 
same as in their cases. The parallel between the older and 
newer basaltic currents visible in such close approximation is 
complete and highly interesting. The only essential difference 
is that of position ; the one occupying the summit of a long hill, 
the others the bottom of its lateral valleys, but yet on many 
points even there forming plateaux which have acquired already 
a very considerable elevation above the actual river-channels. 

The surface of the plateau of La Serre is not a uniform slope, 
being broken by three declivities which have the appearance of 
steps. Two of these are over the granite, and another at the 
line of contact of this and the freshwater formation. They were 
probably occasioned by inequalities in the granitic surface here 
and there opposing a temporary check to the current The portion 
which rests on the freshwater strata is smooth and nearly level 

It is worthy of remark that on each side a transverse ravine 
is found near where the tertiary sedimental beds rest on the 
primary crystallines, and a depression exists on the surface of 
the plateau, along that line, the basalt having been already 
partially undermined there by an excavation sapped through the 
strata of friable sandstone which intervene between the cal- 
careous formation and the granite. In time, no doubt, an entire 
separation will thus be effected, and the eastern portion of this 
hill will resemble the many others around, which have lost their 
connection with the primary heights. 



See p. 92-3 supra. 



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104 MOOTS DOME AND UMAGNE. Chap, V. 

The basalt of this plateau is from 50 to 100 feet in thickness. 
Though in general amorphous, or deft by irregular vertical 
seams, yet on some points, particularly near Le Crest and at 
the Castle of Montredon, it exhibits very beautiful columnar 
groups. The current has here been eaten into by deep ravines 
which disclose its internal structure, and in all probability the 
apparent absence of , this regular configuration in the remaining 
parts of the plateau is only superficial 

Upon the whole, this hill is very instructive, as a type of the 
formation of basaltic plateaux in general ; one of those valu- 
able links which establish a relation between rocks apparently 
remote in geological position; one of the intermediate grada- 
tions through which a current of lava, on its first production, 
occupying the bottom of a valley, passes in the lapse of ages, 
and in virtue of the great resistance it offers (and lends umbrella- 
like to the strata beneath) to the downward wash of rain, into the 
massive and tabular capping of an isolated and lofty mountain. 

72-73. Let Cotes de Clermont and ChanJturgut.— These cal- 
careous hills, once evidently united, and separated now but by a 
shallow ravine, are crowned with a bed of basalt, in nature and 
position very similar to that of Chateaugay ; but its height above 
the plain is greater, and it has suffered more from waste, appa- 
rently in consequence of its superior antiquity. 

It has a gradual slope from the neighbourhood of the granitic 
escarpment towards the centre of the Limagne, and appears to 
have flowed as a lava-current from the heights which rise on 
the north-west of Durtol : perhaps it may have been once con- 
nected with those remnants of basalt which rest upon the granite 
in the vicinity of the Puy Channat, but which have lost all traces 
of scoriae or cellular parts. 

74. Plateau de PrudeUe. — A mass of basalt, which crowns a 
granite promontory impending over the valleys of Villar on the 



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i* *** v-,r.,7 // ft* Vyj Chans*, fait «&kk few kel all trace* 

7 1 /'////*** ,/• /Vw*lfe.— A iam of banh, which crowns a 
^*M/ \tttftiiwiUtrj fm/jwlifig <"<* the valleys of Villar on the 



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Chap. V. ROCKS FROM EARLIER ERUPTIONS. 106 

south and Gressinier on the north, and terminating in an abrupt 
escarpment towards the east. It appears, however, to have once 
extended some way down the steep slope in this direction, for 
many portions of a similar basalt are to be found in situ amongst 
the vineyards which clothe its declivity. 

The cone whence this current flowed still forms a projecting 
knoll at its western extremity, strewed with bomb-shaped scoriae, 
the cavities of which contain delicate stalagmitic concretions of 
quartz, the fiorite of the French mineralogists. It is this hillock 
which occasioned the division of the current of Pariou (6). 

At the point of contact of the granite and the basaltic bed it 
supports, is seen a layer of scoriae, so far decomposed as to be 
cut with a knife ; their cavities are filled with a white and brown 
bole of a waxy consistence. The basalt has separated on some 
points into very regular prisms of five or six sides, which exfoliate 
by decomposition in slaty laminae at right angles to their axes. 

The accompanying engraving gives a vfew of the position of 
this plateau (on the left) hanging over the steep granitic gorge 
of Villar. Beneath is a Boman road, of which the old basaltic 
pavement is still entire (called le Chemin Ferr£). It is formed 
upon the surface of the comparatively recent lava-current de- 
scending from Pariou, since the flowing of which, however, the 
ravine on the right has been worn away more than 150 feet in 
depth. It is evident that the entire gorge has been excavated 
since the basalt of Prudelle flowed upon the surface it now 
covers, which must then necessarily have been the lowest level of 
the vicinity. Here again is a most instructive collocation of the 
older and recent lava-streams, telling the same tale of the gradual 
erosion of the valleys of the district by causes still in operation. 

Though the current of Prudelle has every appearance of 
being single, it consists of two very different species of basalt 
That of the western extremity is remarkable for the numerous 



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Chap. V. ROCKS FROM EARLIER ERUPTIONS. 107 

reous strata of the freshwater formation. Two deep ravines have 
there laid open complete sections of all its beds. The base con- 
sists, like the plain from which it rises, of thin horizontal strata 
of white marlv limestone. At about two-thirds of the whole 




7. Eastern Face of Gergovia, showing its two Beds of Basalt (1, 2), and the stratified Calcareous 

Peperino between them. 

elevation occurs a massive horizontal bed of basalt, in some parts 
40 feet in thickness, which appears to have moulded itself on 
the strata below, and upon the surface of which other calcareous 
strata have been again deposited. 

These, however, though distinctly stratified, and with a general 
tendency to horizontality, are far from being as regularly dis- 
posed as the inferior limestone. They are frequently distorted 
and confused, and occasionally interrupted by narrow horizontal 
venous masses of basalt, which appear to be ramifications from 
the upper bed of great thickness, which surmounts the whole and 
forms the superficies of the plateau. The calcareous strata thus 
included between the two beds of basalt are thickly interspersed 
with volcanic ashes and scoriae. A few thin strata of compact 
yellow limestone may be found apparently free from extraneous 
substances, but the general mass is rather a calcareous peperino 
than anything else. It is in parts veined with semiopal, and 
contains masses of siliceous limestone. 

The lower bed of basalt projects far beyond the upper, appear- 



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Ohap. V. ROCK8 PROM EARLIER ERUPTIONS. 109 

thickly strewed with cellular basalt, scoriae, and " bombs ;" which, 
however, have an aspect of great antiquity. It was, in all pro- 
bability, from this mouth that the currents of Gergovia, Mont- 
fognon, &c, proceeded. Their comparative elevation favours 
this opinion. The Puy de Berz£ measures 3210 feet above the 
sea ; the Puy Girou, 2792 ; and the western summit of Ger- 
govia, 2496. The eastern extremity of the last hill is much 
lower, the whole surface sloping gradually in the supposed direc- 
tion of its flow, L e. from the granitic shore of the lake towards 
its centre. 

80. Basalt of St. Genest de OhampaneUe. — This current occu- 
pies the bottom of a depression in the primitive plateau through 
which runs a small rivulet from the village of Chatrat to that of 
St Genest In its position, consequently, it agrees with the 
lavas of the recent puys ; but since no cone remains to mark its 
source, and it has evidently suffered much degradation, it must 
certainly be prior in date to all these. It is imperfectly columnar, 
and in parts separates into minute angular globules; but the 
circumstance most remarkable in the basalt of this current is the 
large proportion of quartz which enters as an ingredient into its 
composition. This substance is very partially distributed, oc- 
curring in much greater abundance on some parts of the current 
than on others, and presents itself in three modes : 1, as visible 
grains, or imperfect crystals, imbedded in the base ; 2, as a con- 
stituent part of that base, which observed through a weak lens 
appears to be a granitoidal mixture of quartz, felspar, and augite ; 
3, in distinct and frequently large veins, more or less free from 
augite, sometimes entirely pure, of a greyish-white colour, and 
similar in disposition and aspect to the veins of quartz so common 
in Lydian stone, clay-slate, &c This is the only example of a 
quartzose basalt I am acquainted with in Auvergne. 

81. Puy de Chatrat. 82. Puy de Pawedon. — Granitic emi- 



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110 MONTS DOME AND LDIAGNE. Chap. V. 

nences capped by basalt, probably remnants of the same cur- 
rent, but certainly distinct from, and anterior to, that last 
mentioned. 

83. Puy de St. Sandoux. (A. E. 2822 feet) (" Barnfere " of 
Kamond.) — A basaltic plateau, still more elevated but less 
extensive than that of Gergovia. It might perhaps be ranked 
among the dependencies of the Mont Dore ; but as it forms a 
very conspicuous object in all views of the Monts Dome, and 
enters into our map of this range, its description may more 
appropriately find room here. 

It occurs on the limits of the granite and freshwater forma- 
tion, resting in part on each. More than one current appears to 
have contributed to its formation. That which shows itself on 
the surface of the plateau is remarkable for presenting a com- 
plete transition from a coarse-grained dolerite, composed of 
compact felspar and large crystals of augite, to a perfectly 
homogeneous basalt This change is effected both suddenly, so 
as to enter into the compass of a small specimen, and gradually, 
the crystals of augite and patches of compact felspar diminishing 
in size, and the latter being finally superseded by olivine. 

84. Plateau of St. Saturnin. — A basaltic bed entirely on the 
calcareous soil, and at a lower level than that of St Sandoux ; 
but yet, perhaps, a branch of the same current On the south- 
east, immediately above the Chateau of St Sandoux, a portion 
of this bed has assumed the figure of an enormous spheroid, 
composed of columns diverging from the centre of the rock, 
near which they are closely united, to the circumference, where 
a considerable space is left between them. The columns are 
very regular and jointed. On other points the basalt of the 
same bed exhibits a tabular configuration. 

85. Puy cTOUoix. (A. E. 3343 feet)— A conical eminence 
of basalt which apparently is a fragment of the same cnr- 



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Chap. V. ROCKS FROM EARLIER ERUPTIONS. Ill 

rent as the Puy de St Sandoux. It encloses large knots of 
olivine. 

The great comparative elevation of these last three basaltic 
eminences is remarkable. M. Raulin * considers that an eleva- 
tory movement on a line transverse to the general axis of the 
neighbouring mountain ranges has raised them, as well as the 
granitic and tertiary beds on which they rest, since their forma- 
tion. This notion will be discussed in a later page. 

86. Ckox de Coran. — An extensive plateau of basalt resting 
entirely on the freshwater strata, and overlooking the Allier 
from its eastern extremity. On this side, immediately above the 
village of Coran, rises a vast range of basaltic columns, the upper 
portions of which show a tendency to the spheroidal figure. The 
south-western part of the plateau is covered with scoriaB and 
volcanic bombs, exceedingly fresh, and apparently ejected by a 
later eruption which burst through the more ancient basaltic bed. 
A circular cavity, about 30 feet in diameter and 10 or 12 in 
depth, appears to be the only crater left by this recent explosion. 
Its inner walls are perpendicular, and consist of scoriform masses 
of basalt, uncovered by any accumulation of lapilli or puzzolana ; 
an inconsiderable current of very cellular lava seems to derive 
from this point, and clothes the southern slope of the mountain. 
The many fragments of granite imbedded in its scoriae demon- 
strate that this eruption, though undoubtedly of a much later 
date than the basalt which forms the surface of the plateau, 
originated far beneath the calcareous freshwater strata which 
compose the hill. These strata contain veins of gypsum and 
pyrites, interspersed with bitumen or sulphate of barytes. 
Though generally horizontal, on some points they show consider- 
able disturbance, and pass into peperino. The Puy de Coran is 



♦ Bulletin XIV., p. 657. 



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m MOOTS DOME AND LIMAGNE. Chap. V. 

vwrthv of much attention, as including the products of eruptions at 
distinct and very distant epochs ; its scori® abound in octohedral 
crystals of oxydulous iron, in fiorite, and crystals of hornblende 
similar to those of the Puy Channat, but far larger. Some are 
nearly the size of the fist They are occasionally perfect ; but 
in general their exterior is rounded, and the angles blunted as if 
by a partial fusion. 

87. Puy de Cornon. — Two remnants of a basaltic current are 
found upon this extensive and nearly flat calcareous hill ; the 
remaining surface of which is mostly covered by a thick bed of 
boulders of granitic and volcanic rocks, and was obviously at 
one time the channel of the Allier, although elevated between 
400 and 500 feet above this river's actual level. At its base the 
marly limestone passes on some points into peperino. 

To the east of the Allier, between Pont de Chateau and 
Issoire, a considerable number of other plateaux and peaks of 
basalt may be observed, capping eminences both of the freshwater 
limestone and of the low granitic range between the Dore and 
the Allier, against which this formation abuts. These are the 
remaining segments of very ancient currents ; their scoriae have 
generally disappeared ; and the points they derive from, as well 
as their connection, if any ever existed between them, are with 
difficulty to be traced. The space through which they show 
themselves is not very extensive, and may be considered as a 
short band enclosed between the Allier and the meridian of Mozun. 
Nearly all the remarkable hills of calcareous peperino described 
above as part of the freshwater formation of the Limagne are 
also found near these limits. The direction of this volcanic line 
seems to preserve a parallelism to that of the Monts Dome. 

The most remarkable of these basaltic remnants are the Pays 
Bandit, Dallet (already noticed, p. 15), La Roche Noire, St. 



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Chap. V. PICS DE BURON AND MOZUN". 113 

Bomain, Turluron, and St Hippolyte, which are based upon the 
tertiary strata ; and the Pics de Buron and Mozun, which rest 
in part on the primitive soil. They present no peculiar fea- 
tures, and therefore to describe them in detail would only be to 
repeat what has been said already of the similar rocks in the 
immediate vicinity of the Monts Dome. 



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114 • MOXTDORE: Chap. VL 



CHAPTER VI. 

REGION IL— THE MOXT DORE. 

§ 1. General Outline of the Mont Dore.* 

As yet we have found the primary soil concealed but by occa- 
sional masses of volcanic rocks, between which it crops out at no 
very distant intervals. But I have now to describe one of those 
mountainous excrescences which have covered its surface to an 
extent of many miles in diameter, and elevated themselves to a 
proportionate height above its leveL 

The Mont Dore, though not the most considerable of the three 
in bulk or extent, attains the greatest absolute elevation. Its 
highest point, the Pic de Sancy, is given by Bamond as 6258 
feet, exceeding that of the Cantal by 128 feet Its figure will 
be best understood by supposing seven or eight rocky summits 
grouped together within a circuit of about a mile in diameter ; 
from whence, as from the apex of a flattened and somewhat 
irregular cone, all the sides slope more or less rapidly, until their 
inclination is gradually lost in the high plain around. Imagine 
this mass deeply and widely eaten into on opposite sides by two 
principal valleys, (thi**e of the Dordogne and of Chambon,) and 
further furrowed by about a dozen minor water-channels, all 
having their sources near the central eminences, and directing 



* The Mont Dore, anciently Mons properly written Mont <TOr. See Ra- 

Duranius, derives its appellation from mood, SkelUinaU dcs Piames: Mem. 

the stream colled Le I\*re which rises de l'lnst. 1815. 
on iU summit, and is therefore im- 



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Chap. VI. GENERAL OUTLINE. 115 

themselves from thence to every point of the horizon. You will 
then have a rude but not inaccurate idea of the Mont Dore. 

It is barely possible that some mountain, not volcanic, may, 
by long isolation, or accidental circumstances, have assumed 
somewhat of this form, but the additional peculiarity which 
the Mont Dore and Cantai share with JEtna, the Peak of 
Teneriffe, Palma, and all other insulated volcanic mountains, is, 
that the rocks of which each is composed exhibit themselves in 
beds every way dipping off from the central axis, and lying pa- 
rallel to the external sloping flanks. This singular disposition 
would induce us a priori to conclude these mountains to be Jhe 
remains of vast volcanos. The idea is of course confirmed, when 
we discover on examination that they consist of prodigious layers 
of scoriae, pumice-stones, and their fine detritus, interstratified 
with beds of trachyte and basalt, which bear the stamp of an 
igneous origin, and descend often in uninterrupted currents, till 
they reach and spread themselves over the platform around the 
base of the mountain. 

It is true that no regular crater remains on this summit It 
would be irrational to expect one in a volcanic mountain which 
exhibits so many other proofs of having been long and violently 
attacked by the agents of dilapidation since the extinction of its 
fires. 

The fragmentary ejections of its vent have gone in great part 
to form the immense conglomerates that clothe its sides and 
accumulate at its foot Its more durable productions, its lava- 
currents and some consolidated breccias, have more successfully 
resisted the wear and tear of ages, and their highest extremities 
still bristle in elevated peaks over a circus-like gorge, which 
occupies the very heart of the mountain, and was probably the 
site of its central crater, but which now, branching out into deep 
and short recesses, forms the upper basin of the principal valley, 

i 2 



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s> 



116 



MONT DORB : 



Chap. VI. 



and the recipient in which two mountain rills, the Dare and 
Dogne, unite, at the source of the noble river which from thence- 
forward bears their joint names. 

If the materials of a volcanic mountain were arranged in any 
sort of uniformity, the valleys which have reduced the Mont 
Dore to a mere skeleton would exhibit its constitution in the 
most satisfactory manner ; but as might be expected, the sections 
they offer disclose only vast and irregular layers of tuff and 
breccias, mingled with repeated or alternating currents of trachyte, 
clinkstone, and basalt, and traversed by numerous dykes of the 
same rocks,* 

The opposite sides of each excavation generally offer corre- 
sponding sections, the same beds being visible at similar heights 
on both declivities, but varying occasionally in thickness. This 
is universally the case in all the narrower gorges near the base 
of the mountain, where the diminished slope caused the lava- 
currents to increase in width as much as in length ; and in these 
situations the same bed or series of beds often extends over a 
surface of many square miles, forming a succession of vast plat- 
forms, with a slight, and, towards their termination, scarcely 
perceptible declination. 

On examining the currents which compose these distant 



* Were the causes which occasion the 
activity of Mina. to cease, this volcanic 
mountain would before the lapse of many 
centuries assume the chief characteristic 
features of the Mont Dore. Even now, 
its sides are furrowed by deep and vast 
valleys produced by earthquakes and the 
rapid descent of torrents of rain. The 
beds of lava of different epochs may be 
seen forming numerous pseudo-strata 
one above the other, and corresponding 
on the opposite sides of these valleys; 
the most remarkable of which in this 



respect is that of Triaoglietto. See Fear- 
rara, Descrizione ddCEtna, 1818. 

It appears that the flanks of the Peak 
of Teneriffe are yet more deeply in- 
tersected by rents and ravines; and 
M. Escobar is said to have counted 
above 100 strata of different lavas and 
beds of pumice on the sides of the valley 
of las Guanchas, N.W. of the Peak. 
See too the description of the Islands of 
Palma and Madeira in Sir C. LyelTs 
Manual, ed. 1855, p. 498 H tcq. 



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Chap. VI. GENERAL OUTLINE. 117 

plateaux, they are found to consist of basalt* which has flowed 
on all sides to the distance of 15 and 20, and in some instances, 
on the east and north, of 25 or 30 miles from the central heights.* 
Though the continuity of some of these sheets of basaltic lava 
has been destroyed, we may remount many of them without 
meeting any interruption, till at no great distance from the 
summit of the group we arrive at a spot, which, from the torrefied 
and vesicular nature of the basalt, and the number of scoriro and 
bombs ^still adhering to its surface, appeal's to be the source of 
the current, the vent from which it was expelled. 

The plateaux of trachyte, on the contrary, rarely reach to such 
an extent, and few portions of them deriving from the Mont Dore 
are to be found without the limits of a circle of 10 miles radius. 
But what these currents lose in length they make up in height 
and width. The lavas of this class appear to have possessed an 
inferior degree of fluidity to those of basalt ; probably owing to 
their inferior specific gravity f and greater coarseness of grain ; 
and in consequence they have accumulated upon one another in 
prodigious volumes in the vicinity of the source. They thus 
become the most conspicuous if not the most considerable portions 
of the edifice which they have reared in common with the others. 
Trachyte constitutes nearly all the principal heights and central 
platforms of the mountain, while basalt rarely shows itself but 
on its outer slopes or in the lateral escarpments and at the 
bottoms of its valleys. 

A few isolated fragments of basaltic currents may, however, be 



* These dimensions are far from it 40 miles. Spallansani mentions cur- 
being unparalleled by the lavas of rents of 15, 20, and 30 miles (Foy. en 
modern volcanos. '.Sir W. Hamilton Sictlc, i. 219); and Pennant describes 
reckoned the current which reached one which issued from a volcano of 
Catania in 1669 to be 14 miles long, Iceland in 1783, and covered a surface 
and in some parts 6 wide. Recupero of 94 miles by 50 ! (North Qlobe, vol. i.) 
measured the length of another, upon f See Considerations on Volcanos, 
the northern side of iEtna, and found pp. 86, 92, et scq. 



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Chap. VI. ITS CONGLOMERATES. 119 

distance from the centre of eruption ; sometimes spreading into 
wide plateaux, at others filling the bosom of mountain hollows, 
like the masses of drift snow left in a hilly country by a brief 
thaw. 

These conglomerates are susceptible of a division into two 
species, according as either class of volcanic products predomi- 
nates in their composition. 

Some consist wholly of triturated pumice, in which the fine 
silky filaments of this substance are to be recognised, as well 
as a few crystals of felspar. This occurs either loose and 
arenaceous, or consolidated by an intimate mixture with water 
into a yellowish-white tuff of a certain consistence, resembling 
the tufa of the Phlegraean fields, near Naples: occasionally 
it has a lamellar structure, and has been sold in commerce 
for tripoli In general, however, this pulverulent substance 
envelops various-sized fragments of trachyte, basalt, and granite, 
forming a tufaceous conglomerate. As these coarser materials 
predominate, a complete breccia is the result, in which the frag- 
ments are immediately in contact, or separated by occasional 
interstices, or finally agglutinated by a cement, either of tuff 
or of iron-rust, apparently derived from the partial decomposi- 
tion of the fragments themselves, which are in these instances 
for the most part of a highly ferruginous basalt, and in this 
condition it resembles the peperino of the Campagna round 
Rome. . 

M. Bamond, in describing these conglomerates,* very justly 
remarks that their disposition excludes the idea that the waters 
either of the sea or of inland lakes have had any share in their 
arrangement ; t and he imagines them in consequence to have 



* Memoires de Flnstitut, 1815. submarine, it follows of course that 

f The greater number of the extinct the loose matters ejected by them 

volcano* of Italy having been apparently should have been deposited, spread out, 



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120 



MOXTDORE: Chap. VI. 



fallen from the air upon the spot they still occupy after their 
projection by the explosive force of the volcano. 

But it will be difficult for those to coincide fully in such an 
opinion who have remarked that the great proportion of these 
deposits are found, not in the neighbourhood of the crater, but in 
massive and partial accumulations at the foot of the mountain, 
extending frequently in a direct line to a very great distance 
from its centre, without altering their character or suffering any 
corresponding diminution in the size of their fragments. 

The conglomerates which compose the plateaux of Paulines, 
Nechere, and Polagnat, for example, as well as those capping the 
Puy de Monton, are too unequally distributed, too distant from 
the focus of eruption, to have been formed in the manner sup- 
posed by M. Ramond. At the latter point, which is exactly 20 
miles in a straight line from the central summits of the Mont 
Dore, where certainly the vent which ejected them was situated, 
I have observed massive blocks of very compact trachyte and 
trachytic obsidian, measuring more than a cubic yard in bulk. 
It is incredible that fragments of this magnitude should have 
boon urgini to such a distance merely by the projecting power of 
the volcano, a power which is always exerted in a direction very 
noarly if not quite perpendicular. Nor could the prevailing 
winds which, M. Ramond remarks, set that way, have had any 
notahlo effivt upon bodies of so vast a weight We must there- 



Mtai W\*Ued At the bottom or on the Uhl*4and, elevated bUim *X» and | 

ahoraa of the sea: a&d hence the em 5iH\» feet above the actual level of the 

efet «tr*Ufad tuffe of the weetern ooaet tea; a»d who** eartieet eruptuM appear 

of thAt p*toin*uU. from Naj^o* to Chita to have r oeaaaeawed aw* oedj k«ag after 

Ytivhta* See Rrvwhi. ^^ A A\«w, this hued had eskerged froea the mritmt ! 

y^v ts*\ A*v Ac; ttfel l^M^.Ak, 1 .u, rm ooaaax, bat at a period iin the fnah 

, ,„..,v -v^ t water lake* of the dsstrx* had almoet, 

I*m1 the oaa* » wn diSpcvnt evith the if av4 entarohr, 

VoWao* w»hW ovm^W**^*]*, m^Kia poo*** 
i^a»M «^v« th^ Mtm«*Mt « *» tatantaw 



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Chap. VI. ITS CONGLOMERATES. 121 

fore, of necessity admit the agency of some other cause in these 
instances ; and various facts tend to prove that the rapid descent 
of water from the summit of the mountain at the period of its 
eruptions co-operated with the fall of ejected stones and ashes in 
the formation of these conglomerates. 

These facts are principally the following : — 

1. The deposits of this nature, which auvance lo a distance 
from the mountain, occupy a few large valleys, obviously exca- 
vated in the granite or the freshwater strata previous to their 
deposition, and are not found in the wide intervals separating 
these valleys, as would certainly be the case had they resulted 
from the uniform dispersion of loose fragments ejected by the 
volcano. 

2. Their participation in the character of alluvia is evinced in 
the consolidation by water and partial stratification of some of 
the tuffs ; in the occasional layers. and heaps of sand and gravel 
accompanying them, the trunks and logs of trees and the remains 
of land animals frequently found imbedded in them. 

3. The greater number of fragments composing the distant 
conglomerates have their angles broken or rounded, and the 
largest are completely bouldered. 

4. Immense fasciculi of basaltic prisms are occasionally seen 
enveloped by them. The prisms are not separated from each 
other, nor their angles injured. These rocks cannot have been 
launched thus from the crater, but must have been detached from 
neighbouring currents by some violent and erosive attack. 

5. The conglomerates found within the limits of the freshwater 
formation contain rounded fragments of limestone. These could 
not have been thrown up by the volcano, which broke out on the 
granite ; but it is easily seen that the calcareous strata may have 
been torn up by torrents hurrying along and depositing on their 
route the beds enclosing these blocks. 



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122 M01JT DORE : Chap. VI. 

They most not be confounded, however, with the ordinary 
drift deposits of any mountainous country resulting from the 
abrasion of its rocks and excavation of its valleys,— from which 
they are distinguished not only by their volume, but by the 
currents of trachyte, clinkstone, and basalt which cover, support, 
and penetrate them in all directions, and were, therefore, cer- 
tainly of contemporary formation. 

The descent of aqueous deluges down the sides of great 
habitual volcanos during the occurrence of their eruptions, is 
well known to be a common phenomenon,* and to be owing to 
one or more of three distinct causes : — viz. 

1. The sudden melting of snow on the summit of the mountain, 
either by falling showers of red-hot scoriae, or the contact of a 
disgorged current of lava. 

2. Prodigious storms of rain which usually accompany or 
succeed to volcanic eruptions, and have been satisfactorily attri- 
buted to the condensation of the immense volumes of aqueous 
vapour evolved from these vents during their activity, and which 
constitute in fact the main agent in their phenomena. 

3. The vast bodies of water, probably the contents of internal 
crater-lakes, which trachytic volcanos, particularly those of 
America,! are known occasionally to eject, and which, when 
mingled with the ashes and lapilli caught up in their progress, • 
or brought with them from the interior of the volcano, have been 
sometimes called " currents of mud," but must not be confounded 
with the product of those pseudo-volcanic explosions of hydrogen 
gas seen at Macalouba, Modena, in the Crimea, &c. &c It is 
indifferent which of these various phenomena we suppose to have 



* See Considerations on Volcanos, Breialak, Tnxt. Oeol. 9 toI. ill. §.641. 

page 158. Scrope on Volcanos, p. 160. Ljell, 

f See Humboldt, Tableau Physique. Principles, ed. 185S, p. 412. 
Daubuisson, Hcoyn., vol. i. p. 181. 



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Chap. VL ITS CONGLOMERATES. 123 

operated in the present case : possibly all may have been in torn 
or at once brought into action.* 

If we consider the effects that would naturally be produced by 
the sudden rush of large bodies of water down the sides of an 
elevated volcano like the Mont Dore, at its moments of eruption, 
sweeping away all the loose materials surrounding its crater, as 
well as all they meet in their descent, tearing up the flanks of 
the mountain, and overwhelming the plains or valleys around, 
we shall find them fully equal to the formation of the conglo- 
merates that now occupy us, and which, whether filling hollows 
in the mountain's sides, or deep and extensive valleys to a con- 
siderable distance from its base, are found to exhibit just that 
chaotic confusion which we should expect from such a mode of 
production, and which no other can sufficiently account for. 

The Puy de Monton is perhaps the point furthest removed 
from the Mont Dore at which these eluvial products are found in 
abundance. I have mentioned its direct distance from the Pic 
de Sancy as twenty miles ; the difference of level is about 4400 
feet ; a difference which affords an average fall of one foot in 
twenty-four, certainly sufficient to give to any great body of 
water the impetus required for transporting blocks of the size 
already noticed as occurring there. 



* The Mont Dore is covered every volcanoa unite with water into a te- 

winter with great quantities of snow, nacious clay, which circumstance often 

which seldom disappears till late in the occasions the creation of lakes within 

summer. There were some considerable their craters during intervals of tran- 

patches remaining in the hollows near quillity. These lakes either burst their 

its summit when I visited it in the banks by their increasing weight, or are 

beginning of September, 1821, as well as let loose by the next eruption, in either 

at the time of my last visit in August, cose rushing in a tremendous eluvial 

1857. With respect to the occurrence debacle on the lower grounds around 

last instanced, as taking place among the mountain. The trass of the Rhine 

the American volcanos, it is worth volcanos was no doubt produced in 

noticing that, like those of France this manner. — See Considerations on 

under consideration, they are principally Volcanos, p. 159. 
trachytic. The fine ashes of trachytic 



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124 MONT DORE : Our. VI. 

I have been anxious to substantiate the mode of formation of 
these conglomerates, which has not been always satisfactorily 
explained, on account of their forming so prominent a feature in 
the trachytic formations of central France ; constituting perhaps, 
in the three great volcanic groups of this class, a full moiety of 
their whole mass, and appertaining exclusively to these, since no 
similar rock is to be found in connection with the basaltic products 
of the more recent or minor volcanic vents. 

§ 2. Structure op the Mont Dore. 

To describe the constitution of the Mont Dore in detail, rock 
by rock, as far as it can be observed, would swell these pages to 
too great a bulk ; I therefore content myself with sketching its 
principal masses, pointing out whatever is most remarkable in 
them. 

Let us, for this purpose, imagine ourselves for a moment on 
tjie Pic de Sancy, a pyramidal rock of porphyritic trachyte, and 
the highest point of the whole mountain.* Connected with this by 
intervening ridges, rise on each side similar craggy knolls of the 
same substance, more or less rounded by weathering, and partly 
covered with vegetation. One of them, the Puy Ferrand, almost 
equals the Pic de Sancy in elevation. These two most promi- 
nent heights overlook, on our right and left, two deep amphi- 
theatral basins, one opening to the north, encircled with a range 
of perpendicular precipices in which the different sources of the 
Dordogne unite ; the other to the north-west forming the gorge 
of Cliandefour at the head of the valley of Chambon. On the 
side opposite to these hollows each eminence gives rise to an 



* The lootHtie* mentioned in this the Pay de Dome of 1845. Bat see the 
nVoteh of the Mont Dore may be buxTe-eye view of the valley of the 
ttlwrwd iu the Departmental lUf> of Dordogne in Plate VII. 



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Chap. VI. STRUCTURE. 125 

inclined plane with a gradually decreasing slope, perhaps broken 
at first into three or four step-like projections, one above the 
other, and by degrees widening, as it descends, into vast plat- 
forms,* which with few interruptions reach the base of the 
mountain, and prolong themselves to some distance over the 
adjoining country. 

The rock which composes these platforms is, almost without 
exception, trachyte, and the general divergence of all the prin- 
cipal trachytic currents from one spot leads us to presume them 
the produce of a single habitual vent, occupying this central 
situation. The structure of the heights surrounding the gorges 
mentioned above confirms this supposition. They consist of 
various and often-repeated beds of trachyte, exhibiting in their 
confused arrangement and scopform parts features which cha- 
racterize the proximity of a centre of eruption. On descending 
we observe rocky masses of conglomerate alternating with, or 
leaning against them. Of this nature is the high ledge whence 
spring the two rivulets Le Dore and La Dogne, and which unites 
the four chief central eminences, the Pic de Sancy, the Puy 
Ferrand, the Pan de la Grange, and Cacadogne. Immediately 
beneath the Cascade of the Dore, this rock contains alum and 
sulphur in such abundance as to repay the cost of considerable 
works for their extraction. To the west, two deep gorges, called 



* The high lands of the Mont Dore, few fir forests in the highest regions, 

as well as of the Cental and Mezen, are little wood is to be found out of the 

too much exposed and too elevated for valleys; and this peculiar disposition of 

cultivation, but are clothed with an surface and vegetation gives to the 

unlimited succession of rich and widely- country an entirely different aspect ac? 

spreading pasturages. The constitution cording as it is viewed in its valleys or 

of the soil is sometimes thus concealed on the intervening flat-topped heights, 

for a considerable space. It is, however, The former are beautiful, luxuriant, 

always disclosed at intervals in the steep and populous; the latter naked, dreary, 

banks of the water-channels which drain and almost uninhabited, 
the plateaux. Witfy the exception of a 



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126 MONT DORE : Chap. VI. 

Les Vallees de l'Enfer and de la Cour, are completely scooped 
out of the same rock. It has a torrefied aspect, and consists of frag- 
ments of trachyte and basalt, both compact and cellular, united 
into a breccia sometimes by a ferruginous, at others by a pumi- 
ceous cement. In the former case the compound is exceedingly 
solid and durable. It is penetrated by several vertical dykes 
of porphyritic trachyte, of a dark colour, vesicular in parts, and 
divided into regular columns, generally at right angles to the 
walls of the vein. A narrow and low partition, called Les 
Femes, which separates the gorges of la Cour and l'Enfer, prin- 
cipally consists of such a dyke. The enclosing breccia has 
disappeared on one side, but remains on the opposite. In the 
former ravine are two or three others entirely denuded, and 
exactly imitating the ruins of Cyclopean walls ; the extremi- 
ties of the prisms, which are laid horizontally, showing their 
jmlygonal surfaces on each side. The steep face of the Puy 
do FAiguiller, terminating the Vallee de l'Enfer, exhibits three 
or four similar dykes traversing vertically its whole height (900 
feet), and by their needle-like peaks, which rise almost to the 
height of the Pic de Sancy, occasioning its name. 

Immediately opposite to the Vallee de la Cour, on the east side 
of the valley of the Dordogne, is a deep ravine separating two 
craggy cliffs called Cacadogne and Le Roc de Cuzau. It is strewed 
with colossal ruins from the rocks above, which consist of con- 
glomerate enveloping various currents of trachyte and basalt 
mingled in strange confusion. Among the blocks scattered 
UcIqw, and belonging to these currents, are many of a trachyte ap- 
prtHR'liing to obsidian, of resinous lustre and fracture, and a black 
colour, enclosing numerous large crystals of felspar (pitch-stone 
porphyry) ; and another rarer variety, compact, hard, of a brick- 
red colour, with something of the resinous gloss of pitch-stone, 
enclosing opaque crystals of felspar exceedingly hard and of a 



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Chap. VI. ITS CENTRAL CRATER. 127 

waxy look. The roc Barbu, an insulated and shapeless rock 
springing from the middle of the ravine, presents a cluster of 
diverging columns of an extremely dense, heavy, and hard basalt, 
enclosing large and regular crystals of augite and olivine. 

Such is the nature of the area overlooked by the central 
trachytic summits ; and in these features it is easy to recognise 
the traces of a vast and ruinous crater, not very dissimilar to the 
picture exhibited at the present moment* by the recent crater of 
Vesuvius, torn through the bowels of the mountain by the erup- 
tion of 1822 ; whose abrupt and precipitous escarpments, like 
those of the gorges just described, are composed of a conglo- 
merate of scoriae and volcanic fragments, enveloping hori- 
zontal beds of lava, and penetrated . by numerous dykes of the 
same substance, mostly vertical, and separating into horizontal 
prisms. 

We seem then authorized to conclude the principal vent from 
which issued the great formations of trachyte of the Mont Dore 
to have been situated in the immediate vicinity of the upper 
basin of the valley of the Dordogne. 

There is, however, no reason to believe that this vent was 
productive of trachyte alone ; the numerous fragments and dykes 
of basalt enclosed in the surrounding conglomerates, together 



* This was written in 1823. It must the heart of the mountain, or in its 
be remembered that the central crater place a solid dome or cone composed 
of every habitually eruptive volcano of the products of the preceding erup- 
is liable to be alternately emptied tions in the shape of fragmentary ac- 
by paroxysmal explosions, and refilled cumulations penetrated by dykes and 
subsequently by minor eruptions from beds of lava in a state of chaotic con- 
within its area. (See a paper on the fusion. Or the last explosions may have 
Formation of Craters, &c., ' Geolog. only blown up portions of such a cone, 
Proc.,' April, 1856.) The latest erup- occasioning one or more of those circus- 
tions of an extinct volcano may have like hollows so often found towards the 
belonged to one or the other of these centre of such mountains, and of which 
classes, and consequently may either we have examples both here and in the 
have left a vast chasm (or crater) in Cantal. 



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128 MONT DORE : Ciup. XL 

with the direction and slope of the neighbouring basaltic beds, 
tend rather to prove the contrary; and it has been already 
noticed that many of the currents of this rock, so conspicuous on 
the skirts of the mountain, may be traced to points of eruption 
near the central trachytic plateaux, and therefore at no great 
distance from the principal crater. 

If, quitting the circus where the waters of the Dore and Dogne 
meet, we follow the torrent which bears from this point their 
united names,* we find perpendicular cliffs, composed of repeated 
beds of trachyte, bounding the valley on each hand. To the left 
a deep ravine has laid bare the face of a steep rock called Le 
Cliergue, and disclosed the out-cropping of five or six immense 
currents of trachyte, separated from one another by layers of 
tuff and decomposed pumice. The lowest of these enormous 
beds are quarried for the building-stone of the neighbouring 
baths ; and the rock of which they consist is excellently fitted 
for the purpose, separating readily into rude prismatic masses, 
being extremely cellular, working well under the tool, and 
resembling strongly the lava of Nugere or " Pierre de Volvic" 
Its colour is bluish-grey ; it has few apparent crystals of felspar, 
and is highly sonorous. The upper beds are of another variety, 
of a lighter colour, and contain larger and more numerous crystals 
of felspar. 

A similar order of beds is seen on the opposite side of the 
valley. Their upper surface slopes rapidly from the summit 
of the Roc de Cuzau, forming a plateau called La Durbise, 
which is prolonged below in the Plateau de F Angle, imme- 
diately above the village of the Baths. Of this the opposite 
Plateau de Eigolet obviously once formed part, though now 
separated from it by the excavation of the valley of the Dor- 



• See Plate VII. 



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Chap. VI. 



TRACHYTIC PLATEAUX. 



129 



dogne. The height, slope, and direction of each correspond, as 
well as the beds of which they are composed. The upper 
surface of both is occupied by a thick current of trachyte, the 
section of which on each side of the valley presents a long range 
of irregular columns. 




8. Cascade above Moot Dora lea Batna. 

A rent worn through this and some of the inferior beds by a 
waterfall called La Cascade du Mont Dore, at a short distance 
above the Baths, exhibit* them in the following succession : — 

1. (Beginning from above.) A bed of porphyritic trachyte, 
160 feet in thickness, forming the floor of the plateau to its 
extremity. The colour of this stone varies from greyish to 
bluish-white. It bears a considerable resemblance to the rock 
of the Puy de Dome, like which its fissures are sometimes lined 

K 



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ItfO MONT DOBE : CHaf. YI. 

with larg** blades of specular iron. It is highly porous and con- 
tains numerous large crystals of glassy felspar, mica, and acicular 
homhloude envelojHHl in a very loose and coarse-grained base, 
evidently com|tosed of the detritus of these crystals, together 
with gmiua of oxydulous iron and perhaps also augite. It 
ftvs^mhh* strongly the trachyte of Drachenfeh. This rock often 
ouoUw** spheroidal masses, of a darker colour and more compact 
than tW aunxHiiuliug substance, penetrated by interlaced acicular 
omtah* *tf hornMeiuh\ which recall the similar nodules in the 
traohjto \4f the Kuganean Hills and those which occur in some 
£V*nitt* ami iwphvries* 

^v 'VhW tntehvte is superposed to a thick bed of arenaceous 
mfl e\ Mouth Wkttt£tng to the stratum above. In its upper part 
aw h*au\ Khw erystab erf glassy felspar, large and perfect, 
^ywowlh vkml4o. Their outside is mealy ; their interior carious, 
vJVtt ^wuun^ k^v^ttudinal fibres separated by equal interstices. 
V*' vv ^v*nttKv swws to have been produced by a partial fusion, 
vu \ V UMUuor of the filaments of pumice. Similar crystals are 
uM * >\ a iu i ho highly |*wplivritic trachytes of Ischia. 

Cv <\vuutu*r oUataohew passing into basalt,* highly schistose 
m )saU*« v*tf a *Urk slate-colour* unktkling numerous small 
kh\<4*W vtf augite and glassy fVl>jw* It is slightly translucent 
at tfv vsl*^ 

♦ &.«* N*h* pn*t>o«ecl that the ojl"^1 £Jz&fc**co*. In an article pub- 

^ v s*s«*sv ^ >'. s v iw thouUl W *»tabush«d V**ix*i » ti* Jottraal of the Royal Ineti- 

4^!>4 ukK^asv w b*ttdt» which in all t. .:.-.■« *.-e Jkm, l^-S. and containing* 

vw o*'-v* ^.«*ck'« » *>ften liable to joy****?. »-v**v»txtt*I arrangement for 

*v w^avu^vWd with clinkstone and tie .iejrc^cvei jad nomenclature oC 

h^w« Ku« tixu* id impossible, aince to>jc w tw^k I Wtoed to propose 

vl v*> v> i«.v*C v .Htoalt* are to appearance an :£;«rcttt£afi» prans to indode thowe 

> w^s< s^ ttva auwwaL All that can rocks w±.vfe wn** both of the cha>- 

V ^^ * tbt*t ***» T **7 feld»f*thoee ratter* ,tf tt»rhy»» and baemH. to be 

1 k \^* vv*» a'\ r*\^UB*J» trachyte, cal.^i ^viraia* Virwitm'. facta their 

*V ■.*-•** *y*v «;c aad ferru^inoua aa prerju.iac -nifaeil aavanaKe, tart, and 

k s*«* ' *^v * hcJ>\**.* ruck*, when com- I etili 

vs^« *,*s< »«****• w» ttracUnw, being doazraiue. 



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Chap. VI. SECTION AT CASCADE. 131 

4. Breccia of scoriae and volcanic fragments with a cement of 
tuff. 

5. Thick beds of amorphous basalt, varying its characters. 
In some parts of a dark slaty grey colour, compact, sonorous, 
and containing small crystals of felspar: in others, reddish- 
brown, heavy, and close-grained, but studded with large ellip- 
tical cells, the interior of which is generally lined with small 
mammillae of hematite, and the rock is throughout exceedingly 
iron-shot. 

This bed of basalt and its accompanying breccias make their 
appearance also below the* hood-shaped rock of trachyte called 
Le Capucin, on the opposite side of the valley, and in the valley 
of La Scie, supporting that side of the Plateau de Rigolet The 
columnar basalt of the Cascade de la Querilh, at the extremity of 
the Plateau de 1* Angle, which appears to crop out from beneath 
the superficial beds of trachyte and tuff, probably belongs to 
the same lava-current. 

6. White pumiceous tuff enveloping a few fragments of granite, 
basalt, and trachyte. This bed is traversed by two or three 
nearly vertical veins which have evidently proceeded from the 
basalt above ; their lower extremities are seen to terminate in 
the tuff. This and their insignificant proportions oppose all idea 
of protrusion from below.* 



• This remarkable natural section valley, where a vast landslip took place 
presents itself so obviously to all the a few years since, and disclosed the 
visitors of the Mont Dore, lying at the structure of the mountain in a steep 
distance of scarcely a quarter of a mile cliff half a mile in length, a bed of 
from the village of the Baths, and under decided basalt (perhaps the same) also 
the Cascade which is the chief lion of the underlies the mass of conglomerates 
place, that I own myself wholly unable which supports the great upper platform 
to comprehend how M. Beudant and of trachyte. On the whole it may 
other French geologists could in the be said that basalt is as frequently 
free of it have denied the superposition found to underlie trachyte as the ro- 
of trachyte to tuff or basalt. At the verse. It is, I think, impossible to 
Ravin des Egravats, higher up the admit the general priority of the latter 

K 2 



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•ail^i ^L« - ■- "Tjt ^■iiizzair ~£-»r ts* V*nau » ggyi fl W 
■c -»»raL- ia Trrrnz -c -»#rr rrnir *rar!r~i-. imiri i^^at* tar 
a«*r t -l. »--^-£c*i • *U£ok -rulr-i 3*aac ~im iFiufmsgDia rf 
xi»t t I*r "Jtrfrrrte. m^ «ci^a ^-utoir^ *s* imi^ilkJ ia a 

n "^ - •* u: - ^TaCuiius. >i "ut aat & «m? jc .taisr lark 
**=-■*-«— .rr-^ Tin ~Lt* -am? un—tam* *inf jua ;c -viiA gnut<| 
»»- iir ^*u r* — /.rrmviir i' -t-unlmr. 7rrv** xam. *Z to law* 
*r*-a 'Tnrti^l" u^iw ji na* it *at* 3ai*c ! iwihm 1 ad vole- 
nui- -a- ~iaL'^ ~ic J a , "^- , ii3T^nfc *t "in* X-iire Irre. Tie- nvk rf 
»;i_'2 i * --:^- -s^-i > >«Tmifr unt m wv iar^J •^C'^iar; tla* 
r.H^"i *~>*i*a^ t I'tswr iiumariufr ant i*2». «j*MTmtp ere© 
t mr jh at-* n -ruiim- A iiwxce: nae* -raided iTiwrifiar 
jnvii at-* iif i^m liac it Zvsst i.-^peur^ lb? »nL tat at a arah 
.ti^t-r j-v u Auu. & )fc*i it Janat^ :ctKii<k:ue- <n ate fanfare and 
^uiir^ *-ac* ^.« MMiwma^ .if fr*ccce<Kt foam below the 




-i> -tie i rntf :Uei» *i *vn» viuot "Stat 5 

atii V^rtUM' f.'uu> -•■ nr mwnnmo- ^iai ifUMM, «r oil 

M Tif .I'oi*' n <t *. ^tiuuxr & -aas urate lifi^yli w locfa whirfc im difwed m 

•i T3v t-*l*i *n«' «t Mj'OC 7«.t»» W"» Tibr li^vk 

i m n uq ^i r -i ma - ir sttmre^ vijA vxjca haxm * . 

»^ /a iw r uir^r*-. "siwr jwrjj^a* i»i bair ipit. M. Readout, there- 

usn^i a* riwrnn "=bnr >a^k ir xLci !-««. co«ld oeJr intcad to oanfiiie the 

imm- » */ ^rmsiajt-uJiif at v anevrtv » tera lYachyte to * rock of * particular 

W7 iO«r*«*r sn ubzLrv*. a * trar« fccxre ae*i of pecnlkr geolopceJ re- 

Ta.it tMm sc*r r.. '».** - '.-«Mffn *- * — » m htooeja, — e. oouetroctioti b« is not war- 

:!«.€■** 1 1- fm i< *i w» ?' — ' ■* i?.« vix-h notod in patting on * term generally 

Ktsuriif *£** x*ra ;( r..T»E» -.*• * : mrtved in m mineralogical t«nK. — See 

W*s *.*»v tiiW! tax rm. r^ir-tut never .sr»f« <m Vvio/mo*, p.Wrt «e*/. 

f,^.»i ij^v^oi s tL» =i»naer.— The 



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Chap. VI. EASTERN PLANK. 133 

trachyte and tuffs of the upper plateau, though the debris which 
conceal the junction of the two rocks render it difficult to ascer- 
tain the fact 

On the opposite, i. e. the eastern side of the valley of the 
Dordogne, and above the Plateau de 1* Angle, is seen another 
embranchment of porphyritic trachyte of still larger proportions 
than the one just described. It appears originally to have con- 
stituted a massive and elevated ridge (similar to that of which 
we have seen so considerable a segment preserved in the Plateau 
de Bozat), deriving from the central summits of Cacadogne and 
Cuzau, and directed from south to north with a progressive 
inclination. Subsequent denudation, acting with great effect on 
a rock which yields so easily both to decomposition and abrasion, 
has reduced it to an irregular chain of round-topped hills, closely 
united by their bases, and gradually decreasing in height as they 
recede from the central summits. The principal of these go by 
the names of the Puys de 1' Angle, Hautechaux, Barbier, La 
Tache, Poulet, Baladou, TAiguiller, and Pessada At the last 
of them the trachyte abruptly terminates, exactly in face of the 
Monts Ddme ; the interval is covered by basaltic currents, most 
of which appear to me to proceed from beneath the trachyte, 
and to have flowed from the central vent of Mont Dore. 

The plateaux also which descend towards the east from the 
foot of this group, as well as those ' on the southern side of the 
valley of Chambon, which take their rise immediately from the 
Pay Ferrand, are chiefly of basalt They spread with a gradual 
dope, in wide and uniform sheets, over an immense tract of 
country ; at first but slightly furrowed by the mountain torrents, 
ftirther on completely penetrated to the granite beneath ; and, 
as we descend still lower and the valleys deepen, cut up into long 
strips which line the margins of every gorge with massive 
columnar ranges, and project in the form of flat-topped promon- 



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134 



MONT DORE : 



Chap. VI. 



toriee into the plain of the Limagne. These terminate at the 
AUier, but on its farther bank rise some few isolated cones of the 
same basalt, which mark the original extent of the currents, 
and prove that the river had not excavated its actual bed at the 
epoch of their descent They are almost everywhere accom- 
panied by beds of conglomerate equally derived from the central 
volcano, and probably for the most part drifted down to their 
present position by aqueous debacles, such as were referred to in 
a former page. 

The two principal valleys that now drain this vast inclined 
plane, viz. those of Chambon and Besse, partly excavated 
through granite, and partly through the freshwater formation, 
but everywhere bordered by impending ranges of basalt and 
its conglomerates, are exceedingly interesting ; and not the less 
so from the circumstance that the bottom of each has been 
occupied by a current of lava belonging to eruptions of a very 
recent date.* The upper basin of the first-mentioned valley 
exhibits in the overhanging cliffs porphyritic trachyte with con- 
glomerates, resting on granite f and supporting basalt; the 
trachyte terminates above the village of Chambon, but the tuffs 
and breccias accompany the basaltic currents all the way tt> 



• See Plate IX. 

t This U the highest point at which 
the granitic substratum of the Mont 
Dor© shows itself, viz. 3714 feet from 
the sea. It re-appears on the north-east 
of the mountain below Munit It Qwiyre, 
in the valley of the Dordogne, at the 
absolute elevation of 3271 feet; and on 
the south east near Chastriex, of 3422 
feet. If we take the mean of these 
three (3469 feet) for its probable eleva- 
tion beneath the central summits of the 
mountain, we shall have 2748 feet as 
the depth of the volcanic products alone 
on that point, and above 14oo feet for 



their average thickness throughout a 
central circle of 3 J miles radius. 

This volume, however considerable, 
is far inferior to that of the Cantal, 
perhaps scarcely exceeds that of Ve- 
suvius, and sinks into nothing when 
compared with the colossal bulk of 
Mtna, or the Peak of Teneriffe, which 
consist principally of volcanic matter 
from the level of the sea, and indeed 
from a great depth below this, to the 
height of 1 1,<H>0 and 12,000 feet: or the 
still more stupendous trachytic for- 
mations of the Andes and Cordilleras. 



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Chap. VI. NORTHERN PLANK. 135 

the AlHer, showing themselves at intervals throughout both 
valleys in prodigious accumulations, as in the Dent du Marais 
near the Lake Chambon, and the plateaux of Pardines and 
Nechers. 

They universally contain blocks of every variety of trachyte 
and basalt, fragments of granite, pumice-stones, scoriae, &c., and 
a large proportion of titaniferous iron in their sandy detritus. 
Masses of limestone occur in them where they cover or rest 
against the freshwater strata ; and in similar circumstances the 
basalt has sometimes its cellular cavities filled with calcareous 
infiltrations. At the Montagne de Laveille, near Chidrac, some 
highly amygdaloidal portions occur, in which arragonite and 
carbonate of lime form nearly two-thirds of the mass. It is 
immediately beneath, or occasionally intercalated among, these 
tufls and breccias thkt the celebrated bone-beds of Motit Perrier 
occur, in which Messrs. Croizet* Bravard, and Pomel have de- 
tected numerous mammalian remains belonging to several 
distinct assemblages of species, which the two former naturalists 
refer to successive tertiary epochs.* 

The Dordogne, which for the first three or four miles of its 
course flows nearly from south to north, makes a sudden bend 
to the west a short distance below the village of the Baths, 
leaving to the right a massive portion of high table-land which 
exactly fronts the whole of its upper valley, and was perhaps 
originally separated from the central heights by some violent 
explosions, while the subsequent excavation of the channel of 
the Dordogne has widened the breach. 

The base of this mountain consists of various conglomerates, 



* See Sir C. Lyell's Manual, p. 552, of Organic Remains of Central France 
ed. 1855 ; and Quarterly Journal Geol. in Appendix infra. 
Soc, vol. ii p. 77. Also the Catalogue 



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136 MOXTDORE: Chap. VI. 

enveloping beds of basalt; above these a band of clinkstone 
may be traced across the whole of its eastern and northern 
faces, surmounted by porphyritic trachyte — if indeed these two 
rocks do not, as might from many circumstances be suspected, 
pass into each other. Finally, the upper surface of the plateau 
exhibits more recent currents of basalt, which appear to have 
had their origin there. 

Trachyte, however, occupies by far the most conspicuous place 
amongst these rocks, constituting the Puy Gros, an enormous 
flat-topped boss on the eastern summit, and descending from 
thence to the west in a wide unbroken platform, though occa- 
sionally covered by basalt, as far as the village of La Queuille, 
where the current terminates in a range of gigantic six-sided 
columns, some of which I observed to be not less than 15 feet 
in diameter ; their height is not proportioned to so great a bulk, 
rarely exceeding 30 feet The rock which composes them is a 
dark-coloured trachyte approaching to basalt (greystone), im- 
bedding felspar and augite crystals, and exceedingly cellular. 
Its largest cavities often contain radiated crystallizations of 
arragonite. 

Clinkstone, or the laminar and scaly species of trachyte, pre- 
dominates to the north of the Puy Groe, where a thick bed of it 
seems to have been separated into detached segments by the 
torrent which flows from thence to Rochefort The largest of 
the masses thus isolated are the Puy de Loueire, and the Roches 
Sanadoire and La Tuiliire. At the first the phonolite is 
divided into compact tables ; at the two last rocks, into very 
regular prisms. Those of Sanadoire are entangled into fantastic 
groups, in one spot diverging so regularly from a common centre 
as to resemble a circular fan. The prisms of La Tuili&re are 
vertical or nearly so, and schistose, splitting into thin lamina?, 
which at the northern extremity of the ruck are at right angles 



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Chap. VI. NORTHERN FLANK. 137 

to the axes of the prisms, but acquire gradually an increase of 
inclination, till at the other end their obliquity is such that 
their planes make an angle of but 15 or 20 degrees with the 
axes, and the agency of gravity co-operates with that of the 
weather in separating them : the rock on this side is in con- 
sequence completely in ruins. These plates are used as roofing- 
slates throughout the neighbourhood, and hence the name of 
La Tuilifere. 

This clinkstone contains occasional crystals of felspar, and 
assumes in parts so much of thei aspect of trachyte, that I am 
inclined to suppose it but an accidental variety of this rock, 
more particularly as the bed to which it belongs appears to 
merge in the great trachytic currents of the Puy Gros on one 
side, and the Puy de rAiguiller on the other. 

The volcanic nature of the Roche Sanadoire was at one time 
strongly contested by naturalists, who examined the individual 
rock or its specimens alone, without consulting its evident con- 
nections with those around. But the frequent occurrence of 
cellular portions, and occasional scoriae imbedded in its prisms, 
might have sufficed to convince even these sceptics of its igneous 
origin. Dr. Weiss of Leipsic discovered grains of haiiyne in 
this rock, but they are almost microscopic, and very rare. 

The basalt of the high plateau now under description appears 
to have been produced by repeated eruptions from a vent to the 
north-west of the Puy Gros, the site of which is marked out by 
two elevations entirely of scoriae, called Chantouzet and Le Cros 
de Pize. 

Its currents have flowed both to the east and west, forming on 
one side the margin of the lake Gu&ry, on the other descend- 
ing into the valley of the Dordogne, and exhibiting many 
prismatic ranges along its banks, as far as St. Sauve. They 
are accompanied by breccias, and may be observed at Murat le 



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t» BOOT IKK: <Ja*r. TL 

Quay**, le lioe de la XantOhe, and other pmte. "to he aiyu - 
jiwwd to « thidk bed i/md»ag fresh in aspect w^Meflfflf 
veoaut volcano. 

A *till more exteaiarre aeries of bamhir ca n rants «trefcm«t 
&um the foot of the Pot de F AigmTkr toward* tie wife. 
K»ehiug to the distance of 1<j mike along the Wok of lie 
Kioule, aud covering ?tm* part of the granitic platen nf tke 
Moat* Dome. Here, as elsewhere, they are found m ; 
with the c<niglom€ra&e&. whkh i oo ony cnr them in 
titie« alu*** to the end of then- eoone. A vide basin parallel 
to the granite mage of the Haute Dome appeal* to kave beea 
oaee completely filled by tkeee united volcanic prodorts. rf 
which immense port*** still remain there. At Polognat the 
twff oousiats principally of very white and si!ky pmnice^ftcmes 
evidently (gratified br water. The congl o m erates of tins ini^- 
boorbood oot uiifrequently enclose trunks of trees, in which a 
complete pa*»ge may be traced from ample wbraamtima to 
the state of jet They also contain grains of snlpbar b e ia w a 
their fibre*. 

The variety of btwaltic currents which hare taken this direc- 
tion i* remarkable. Near Rochefort they form repeated and 
enormous beds, divided into very regular prisms or table*. The 
hitter niodifk-ation of structure is also exhibited in perfection on 
tlie border of the valley of the Simile opposite St. Bonnet where 
taUjlar ma**'H are often extracted ten feet long and propor- 
tionately wide, with a thickness of bat three or four inches. 
Their aurfa*** are smooth and level; they are exceedingly 
elastic, and ring upon being struck exactly like a plate of cast 
iron. The basalt of which they consist approaches to clinkstone, 
i* fine-grained and highly crystalline, perfectly compact of a 
lifdit slate-colour, with a tinge of green, and totally free from 
any imbwMcd crystals, though an imperfect agglomeration of 



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Chap. VI. SOUTH- WESTERN FLANK. 139 

augitic particles into globular concretions is betrayed by weather- 
ing. Near Villejacques, in the same valley, a current makes 
its appearance from amongst the surrounding tuff, the basalt of 
which encloses brilliant laminar crystals of hornblende some- 
times two inches in length, and granular ones of olivine. It 
decomposes into minute angular spheroids. Another neigh- 
bouring current is formed of a very fresh and cellular basalt, 
resembling some lavas of the chain of puys ; another is highly 
impregnated with iron, black, dense, and heavy. 

The south-western face of the Mont Dore remains to be noticed. 
It presents a more uniform and smoother slope than the others. 
The currents of trachyte have proceeded but a short distance in 
this direction from the central heights. They constitute two 
or three salient masses composed of a porphyritic rock more 
or less porous, and in the vicinity of the supposed crater even 
scoriform and tinged of a deep red colour. Basalt on the con- 
trary is extremely abundant on this side. It descends in 
extensive plateaux, from the extremities of the trachytic beds, 
and accompanied by a breccia of scoriae on which it gene- 
rally rests. Wherever these plateaux have been channelled by 
torrents, their sections offer ranges of columnar prisms of the 
greatest regularity ; as at Chastreix, La Tour d'Auvergne, &c. 
At the latter spot the prisms are jointed, fitting together by 
means of alternately convex and concave bases ; when broken 
they disclose a cylinder of compact and black basalt within a 
prismatic case of a lighter colour and looser texture. 

The limits of the Mont Dore on the south are not very definite. 
The prolongation of its base meets that of the Cantal, and unites 
with it in forming a high and massive table-land, which divides 
the waters of the Dordogne and AUier, and is known by the 
name of Les Montagues de Cezallier. A scanty vegetation 



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Chap. VI. RECENT ERUPTIONS. 141 

the formation of an expanse of water, called the Lake of Cham- 
bon,* which appears from the flat and alluvial surface of the 
plain above to have been originally much more considerable, 
and to have retreated gradually in proportion to the excavation 
of the channel through which its excess is now discharged. 

Although the hills on each side are loaded with the ancient 
volcanic currents of the Mont Dore, granite shows itself con- 
tinually at their bases ; and it is through this rock that the 
eruption of Tartaret has taken place, displacing and tearing up 
a superficial bed of basalt, which appears to have pre-existed on 
the spot 

The cone is composed throughout of loose scoriae, lapilli, and 
fragments of granite. It has two deep and regular bowl-shaped 
craters, separated by a high ridge, and each broken down on one 
side. They have furnished together a very copious lava-current, 
which at first spreads over a wide and level surface, then, con- 
tracting itself as the valley becomes narrower, occupies the 
channel of the former river, and follows all its sinuosities as far 
as Nechers, below which it terminates at a distance of thirteen 
miles from its origin. 

It is an interesting study to follow, through so long a course, 
this current of recent basalt from its source within an indisput- 
able volcanic cone, along the bottom of a valley cased partly in 
granite, but whose sides are everywhere fringed by sections of 
more ancient currents, which have flowed in the same direction ; 
to observe the analogy of these basaltic formations of different 
epochs, their perfect parallelism and almost equal extent, at 
least in one direction ; their frequent similarity of structure ; for 
in many parts, particularly near Champeix and Nechere, the 
more recent basalt is divided into regular columnar prisms; 



* See Plate IX. 



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142 MONT DORE: Chap. VL 

their common mineralogical characters, and the scoriform parts 
that accompany each. 

There are few known countries in which such admirable juxta- 
positions of ancient and recent volcanic products are to be found ; 
and hence, perhaps, the repugnance long exhibited by those 
who had only examined the extremes of the series at remote 
spots and distant periods, to admit their identity of origin. Here 
Nature herself has brought together the objects of comparison 
and placed them at once before the observer's eyes, as if for the 
express intention of teaching him their common mode of 'forma- 
tion. In the words of M. Ramond, " Ce n'est assurement pas 
au Mont Dore que la fameuse question de la Volcanicit6 des 
basaltes sera jamais l'objet d'une discussion s&ieuse ! " * 

The village of Murol is built upon the recent current at the 
base of the cone, and the space covered by the lava to the south 
is dotted with between thirty and forty black and shapeless 
eminences of scoriform basalt, which, rising from an otherwise 
smooth surface (for the intervening spaces have been brought 
into cultivation), offer a singular and striking picture. The form 
of the valley renders it extremely probable that, at the period 
of the eruption of Tartaret, there existed some stagnant body of 
water in this corner, which would account in a simple manner 
for these protuberances, it having been observed that such irre- 
gularities of surface are liable to be created whenever a current 
of lava meets in its progress, or rather rolls over, any marshy or 



* Written in 1823. In the present was considered heresy to dispute the 

day it seeins almost incredible that up precipitation from some archaic ocean 

to so late a date the igneous origin of all the crystalline rocks. And as it 

of banalt ahould still have been con- was felt that the primary crystallinea 

tested by geologists of repute. But the could hardly be separated in the cha- 

school of Werner was even then pre- racter of their origin from the trap 

dominant in Germany, at Edinburgh, rocks, the battle was fought about 

and in several other quarters, where it these. 



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Chap.. VI. RECENT ERUFflONS. 143 

moist ground : the conversion of the water into steam causing a 
series of violent explosions, and thereby tearing and driving 
upwards portions of lava, which are immediately consolidated in 
ragged and fantastic forms by contact with the air. 

The basalt of Tartaret is compact, of a harsh texture, a dark 
colour, and contains crystals of augite, olivine, and numerous 
minute laminae of felspar. The adjoining conical eminence upon 
which rises the ruined castle of Murol is of ancient prismatic 
basalt, a detached segment of one of the currents which skirt 
the valley on each side. 

The Puy d'Eraignes, seen beyond in our sketch, is of the same 
nature ; both owe their insulated position to the erosion of con- 
fluent mountain torrents. 

Two recent cones, called Montchal and Mont Sineire, occur 
next in succession towards the south ; they have exploded through 
repeated beds of basalt, and probably trachyte, at a considerable 
elevation on the flank of the Mont Dore. 

Both have large and regular craters, and both have produced 
abundant currents of lava, which enter the valleys of Besse and 
Compains, and thread them for an extent of some miles, resting 
indifferently on former beds of basalt or on granite. The furious 
torrents of both gorges have in turn eaten out a fresh channel 
from the recent basalt to the depth often of 30 and 40 feet The 
current proceeding from Mont Sineire in particular is of pro- 
digious bulk and extent 

One remarkable and peculiar circumstance attends these 
cones ; viz. the existence of a deep, large, and nearly circular 
hollow immediately at the foot of each. The bottom is covered 
with water, and they bear the names of the lakes Pavin and 
Mont Sineire ; both are bordered by nearly perpendicular rocks 
of ancient basalt Their position announces them to be contem- 



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144 RECENT ERUPTIONS OP MONT DORE. Chap. VL 

pantry with the eruptions of the neighbouring cones; and it 
seems probable that, like the Gour de Tazana already described 
amongst the Monte Dome, they owe their formation to some 
extremely rapid and violent explosion. 

In the same neighbourhood are several other minor cones of 
scoriae, and four more crater-lakes, named Chauvet, Beurdouze, 
Champedaze, and La Godivel ; which are probably owing to a 
similar cause, and date from about the same recent sera of sub- 
terranean activity. 

A few other recent eruptions have taken place to the east 
of the same meridian ; viz. in the neighbourhood of Coteuge, 
Bantieres, Brion, &c. ; presenting the usual characteristic pro- 
ducts already described on so many other points, the repetition 
of which may be as well omitted. 

They are confined to the south-eastern slope of the Mont Dore, 
and none are to be found within the boundaries of the Cantal, 
which is out of the direction of the zone along which the most 
recently active vents are alone distributed. 



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Oha*.VII. CANTAL. 146 



CHAPTER VII. 

REGION III.— CANTAL. 

§ I- 

In original constitution and form the immense volcano whose 
remains occupy nearly the whole extent of the present depart- 
ment of the Cantal must hare very closely resembled that of 
the Mont Dore ; and the two groups, as they now exist, differ 
little in the nature of their erupted materials. 

In figure the Mont Dore was described as resembling an 
irregular depressed cone : the Cantal approaches still nearer to 
it, since its sides slope more uniformly from the central heights. 
The chief circumstance to which the irregularities in the outline 
of the former mountain are obviously attributable is the excessive 
bulk of the hummocks of trachyte which the volcano has pushed 
forth in three or four directions. The trachytic lavas of the 
Cantal, on the" contrary, perhaps in consequence of a superior 
degree of fluidity, have reached to a considerable distance without 
accumulating into such enormous masses, and have been sub- 
sequently covered by repeated and widely spread sheets of basalt, 
which give to the skirts of the mountain a more regular and 
gradually sloping surface. '* 

The valleys by which this surface is intersected ^stretch out 
like rays on every side from the central heightafonto the sur- 
rounding country ; they are generally deep, a^d bounded by 
steep and rocky walls exhibiting on each side corresponding 

L 



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14(5 OANTAL. Chap. VII. 

sections of the different volcanic beds through which the excava- 
tion has been effected, and, towards their termination, cutting 
into the primary base by which these are supported. 

Such are the great western valleys of the Goid, Cer, Marone, 
Mars, and Rue, which pour their waters into the Dordogne or 
Lot; and that of the Alagnon on the east, the only stream 
which the Cantal contributes to the Allier. We have already 
described the calcareous freshwater formation which within a 
limited space is interposed between the primary crystalline 
rocks and volcanic superstructure. 

The lowest bed of this last formation generally consists of con- 
glomerate. It is seen at the bottom and sides of every deep valley, 
often constituting a vast and imposing range of turreted cliffs, 
which, in consequence of a rude columnar division on a large 
scale, assume various fantastic forms. The bulk and extent of 
this bed are alike surprising. It is found in some valleyB, that 
of the Cer for instance, continued with a constant thickness of 
several hundred feet from the base of the central summits to the 
distance of more than twenty miles ; preserving everywhere a 
gradually diminishing inclination parallel to the sides of the 
mountain. It universally envelops or is accompanied by cur- 
rents of basalt and trachyte, which show themselves at intervals 
without any regularity, and are often intimately blended with 
the neighbouring conglomerate. The constitution of this rock is 
more varied and disorderly here even than at the Mont Dore. 
In one spot it consists of a loose arenaceous tuff enclosing 
bouldered blocks of trachyte, basalt, and granite ; in the next, 
of a consolidated ferruginous breccia of angular fragments of 
basalt and scoriae, sometimes united by a cement of basalt itself, 
sometimes, within the limits of the freshwater basin, by a cal- 
careous or argillaceous one. Occasionally the most decided 
indurated tuff containing angular fragments graduates into a 



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Chap. VII. CANTAL. 147 

compact rock enclosing small crystals of glassy felspar and augite, 
having a tendency to a prismatic rhomboidal divisionary struc- 
ture, and stained throughout by the oxide of iron in stripes of a 
brown colour exactly imitating in their arrangement the undu- 
lating and parallel zones of a fir-plank.* On other points all 
fragments are absent, and the tuff is indurated, obviously by 
water, into a laminated shale, full of impressions of leaves and 
branches of trees, and sometimes passing into an earthy lignite, 
which is used by the peasants as fuel. 

These different modifications of composition, as well as the 
position and appearance of the great beds of conglomerate, are 
reconcileable with no other mode of production than that to 
which was attributed the same order of rocks in the Mont Dore. 
Their formation was obviously contemporary with that of the 
lava-currents they envelop ; but their nature and extent preclude 
all idea that they are owing solely to the projections of the 
volcano; while the great elevation which they attain round the 
central heights refutes the supposition of their being merely 
alluvial deposits from any body of water which may have existed 
at the foot of the mountain during its eruptions. It only remains 
then to conclude them the result, for the most part, of torrents 
of water tumultuously descending the sides of the volcano at the 
periods of eruption, and bearing down immense volumes of its 
fragmentary ejections, in company with its lava-streams. 

These vast beds are usually surmounted by currents of basalt ; 
sometimes, as in the valleys of St. Paul de Salers and Falgoux, 
repeated five or six times, and separated from each other only by 
a layer of their own scoriae. I noticed no instance of beds of 
trachyte alternating with basalt, as was observed in the Mont 
Dore. Throughout the Cantal the production of the former 



* Analogous to the regenerated trachyte observed in Hungary by M. Beudant. 

L 2 . 



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148 CANTAL. Chap. VH. 

rock, with its associated tufas and breccias, seems to have ceased 
before the eruptions of basalt commenced. 

Such, at least, is the general order observed in the sections 
afforded by the principal valleys, at some distance from the 
, summit of the mountain. On a further ascent, the confusion of 
products becomes greater, indicating the vicinity of the vent 
of eruption. The conical form of the whole mountain, and the 
divergence of all its currents from the neighbourhood of a few 
central heights, leads, as in the case of the Mont Dore, to the 
presumption that the volcano of the Cantal had one principal 
and central crater ; and many circumstances unite to fix the 
situation of this upon the double basin in which the upper 
sources of the rivers Jourdanne and Cer are first collected. 

It is from the outer circuit of this area, encircled by several 
culminating peaks and ridges of trachyte, that the chief volcanic 
currents appear to originate. In the centre rises the Puy Grioa, 
separated from a mass of clinkstone, the Plomb du Cantal, by 
a considerable depression, across which passed the old road from 
Murat to Aurillac, now superseded by a tunnel bored through 
the connecting ridge at a level 9(X) feet lower. The Plomb, the 
highest point of the whole mountain (6258 feet A.E.), is of 
basalt, and thence probably proceeded the enormous basaltic 
currents which have flowed towards the south-east 

In piercing the tunnel mentioned above, a great number of 
more or less vertical dykes were met with, of trachyte, clink- 
stone, and basalt,* traversing a breccia containing cellular and 
8coriform fragments of these rocks, as well as veins of green 
pitchstone porphyry. This structure, so similar to that of the 
centre of the Mont Dore, is just what we should expect to find 
in the eruptive chimney of a volcano, t 

• See a paper by M. Ruelle, Bulletin xiv. p. 106. 
f See note to p. 127. 



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Chap. VII. BASALTIC PLATEAU— LA PLANEZE. 149 

The eminence called the Col de Cabre overlooks the source 
of the Jourdanne on the north, giving rise to a mountainous 
embranchment principally consisting of trachyte, which extends 
in a north-easterly direction, and separates the valleys of Murat 
and Dienne; while to the N.W. of the same area the Puy 
Man stands at the head of powerful and repeated currents of 
basalt, which, accumulating on one another, form the Montagnes 
de Salers, and spread from thence over a high plain towards the 
Mont Dore. 

Indeed, with the exception of the masses already designated, 
and a vast but considerably degraded current of the same nature 
which terminates in an enormous and elevated plateau above 
the town of Bort on the west of the Dordogne, resting on a 
layer of pebbles, and apparently occupying the former bed of the 
river which now flows more than 1000 feet below it; — with these 
exceptions, the trachytic lavas of the Cantal are far from con- 
spicuous on the exterior of the mountain, and are greatly ex- 
ceeded in number, volume, and extent by its beds of basalt, 
which stretch in all directions from the central eminences over 
its sloping skirts, and on the east and south-west reach to 
distances of 25 and 30 miles. 

To the south-east they form an extensive and uniform high plain, 
called La Planeze, reaching to the base of the primitive range 
of La Margeride, but little farrowed by watercourses, and of a 
singularly dreary aspect from its total nudity. At its extremity 
is seated the departmental capital St Flour; and here, as 
wherever else this plateau is broken through, successive and 
parallel beds of basalt may be seen surmounting one another in 
very regularly columnar ranges. 

A series of similar plateaux extends from the mountains behind 
Salers to the town of Mauriac, and thence some w#y northward. 
They consist principally of a light-coloured basalt, with a highly 



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150 CANTAL. Chap. VH. 

crystalline grain, sprinkled with large cellular cavities. It 
exhibits on different points the columnar, the tabular, and sphe- 
roidal concretionary structures ; and wherever it has yielded to 
the erosion of torrents, is seen to rest on a tuff conglomerate. 

But the basaltic beds through which the Alagnon has exca- 
vated its valley in the immediate neighbourhood of Murat are 
the most remarkable of all for their regular columnar configura- 
tion, no less than for their bulk. 

They are associated with trachyte, accompanied and in part 
enveloped by accumulations of breccia ; but on particular points 
colossal portions of basalt have been stripped of these coverings 
and isolated from the remainder of the current to which they 
belong. Such are the Montagnes de Bonnevie and ChasteL 
The former, at whose foot stands the town of Murat, has been 
long celebrated for the beauty of its columns. It is a large 
conical rock, about 400 feet in height from its base, composed of 
a single enormous bundle of prisms converging from all sides 
towards the apex ; those of the exterior being slightly curved, 
the central ones straight and vertical. These last are the most 
perfect, and have been exposed by dilapidation on the eastern 
side of the rock. They are smooth, long, and slender, usually 
six-sided, rarely exceeding 8 or 10 inches in diameter, with a 
height often of 50 or 60 feet unbroken by joints or flaws. The 
museums of Paris and Lyons, as well as many private cabinets, 
have been enriched with columns extracted from hence ; but it 
ia a work of extreme delicacy to separate them whole from the 
riH-k, ami still more difficult to convey them uninjured to any 
■list ;mtv. This basalt is brittle, sonorous, hard, compact, fine- 
grained, of a dark colour, and free from any visible crystals. It 
is remarkable that the western face of the rock is entirely 
amorphous.* 

• See Plate X. 



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' *%;■ 




X 



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1 



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Chap. VII. BASALTIC PLATEAUX. 151 

On the contrary side of Murat is a segment apparently of the 
same bed, in which the columns are subdivided by frequent 
joints ; the separate articulations fitting into each othe; by means 
of alternately concave and convex bases, having occasionally 
small wedge-shaped processes arising from the odd angles of 
one prism, and closing over corresponding oblique truncations 
in the other. 

Both above and below Murat, in the valley of the Alagnon, 
patches of the lacustrine limestone are quarried for use beneath 
the volcanic rocks, proving the freshwater formation to have 
extended to the east of the central vent of the volcano. But its 
chief bulk is seen on the opposite or western flank, where in the 
vicinity of Aurillac * a thick bed of breccia, alternately sup- 
ported, covered, and penetrated by currents of basalt and trachyte, 
rests upon the siliceous marls and limestones, the strata of which 
are in many spots twisted and dislocated, as if they were still 
unconsolidated at the moment of their invasion by the volcanic 
torrents. Occasionally there are appearances of a subsequent 
deposition of limestone in confused strata moulded upon the rude 
surfaces of the volcanic beds. This may be observed between 
Polminhac and Yolet in the valley of the Cfer. In general, how- 
ever, the line of junction of the lacustrine formation and super- 
imposed volcanic products is better, defined ; it may be followed 
almost uninterruptedly from Vic en Carlad&z to Aurillac. The 
currents both of basalt and trachyte occasionally send out thick 
vertical veins or dykes into the limestone below; but neither 
along the walls of these, where the contact of the two substances 



* It is said that a sufficient quantity river derives from hence its name: qu. 

of gold-dust was less than a century Auri locus ? The trachytes of Mexico are 

ago contained in the sand of the river auriferous ; there is nothing therefore 

Jourdanne to repay the labour of sifting improbable in the idea that those of 

and washing; and tradition asserts that France may be so likewise. — See Brieude, 

the town of Aurillac situated on this Top. Medicate de CAutcrgne, 1782-83. 



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162 CANTON D'AUBRAC. Chat. YIL 

is immediate, nor elsewhere, could I trace any material alteration 
in the texture of the limestone. Infrequent instances calcareous 
masses, as well as smaller fragments and even some freshwater 
shells, may be seen enveloped by the lava, but they still effervesce 
briskly with acids, and, except in a somewhat dusky tinge, seldom 
appear at all affected. 

The lacustrine beds are found at a higher level, by several 
hundred feet, on the east side of the mountain, than on the west, 
which led Mr. Baulin* to suppose the existence of a fault tra- 
versing the central heights of the mountain, and dating ite forma- 
tion from the first outbreak of the volcano— a supposition by no 
means improbable. 

Without the limits of the tertiary formation, the primary base 
emerges from beneath the volcanic products on every side of the 
CantaL The most elevated point at which I have observed it is 
near the village of Thi&ac in the valley of the Cfer, between five 
and six miles from the supposed crater, where a rock of gneiss, 
certainly in situ, pierces through the calcareous strata as well 
as the overlying trachytic breccia, and disappears again imme- 
diately. 

We have no data by which to determine the relative ages of 
the volcanic remains of the Mont Dore and CantaL Appearances 
would lead to the conjecture that these volcanos were occasionally 
in action at the same period. 

§ 2. Canton d'Aubrac. 

The small mountainous district of Aubrac, which lies between 

the three towns of La Guiolle, St Geneis, and St Arcize, in the 

department of Aveyron, is for the most part covered by massive 

beds of basalt, which belong, I believe, to a centre of eruption 



* Bulletin xiv., p. 174. 



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Chap. VII. CANTON iyAUBRAC. 163 

independent of that of the Cantal ; but having had no oppor- 
tunity of observing this group otherwise than from the summit 
of the latter mountain, I am unacquainted with the true limits 
and disposition of its volcanic productions. I am, however, 
assured by M. Le Coq, who has visited it, that the basalt has 
been evidently erupted from the gneiss and mica-schist on the 
spot, and that no traces of any tertiary or other calcareous strata 
are to be seen there. 



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TW|i KK JL "Ilr-X" II* £~«* 1* T^tr **C S&£ tWTHLlj-eart \w tfce 

Vi3 tctiiiu"" rv^?* r La \ut*t .«-.. ^nn-mri- Mat* dttftrkd 

inratflr uni Tie a ^airrarir «f ^ie Ziuin* L-anr t*r li* kig4 

it*t; if. rnainr ^d* ir^-srii^ i* lift i»t-**x. nruri 

i^ ijcrriii> a*-v*eiiJ:::r imh. ii* i*-*irtiir of La i^iiutK- I*itm. and 



ti'iwe of "mr. «r~~ iut Im» fcii^it. ca..j w*et a- -minm— ." It xtx tiv 

iruo. ~llm rjmjL iKinr ua?*' :wnt«L r*f afi*- tr^ nntr v» iwxuk. "si* ., tL» 

cur.* .*■ xi»^^li«ifc "Uk i.r-.^n --cr ziu :,- o t* ^ mn ii« r**«- tenv jb*d- 

x^Ilur ar "•"*«!* Isv.utt. or* if i:w *» - w*i^a». x- xiu xm* ibt ^rtvm 

■or: a Lur-Tit h c-ajstsfr «i: i snu:* «■. ■!»!*- luiiu^ am ou r » i- ht b*^«d 

miuearr^ «rti i «r«jr ■*: ::> t«wi uiu n. m duiw* mt ta» «mr» h«« imlt 

*u*uui U*» mcmiitaen; an*!, at.in hl k* b*im v b -m*. nft 

tlwnaii'A 1* w nuill » ettr.7 » tut icuu*J. tte »»nt» 41* Uh 7&i*«»r fcndcc» 

..»u wnr.ir7 tun xt ir mrr wiiim. m im»t-'; r<mjjit(n<SL «: ih>«vc, t»*t Vm 

i«-T \«m ioic imder Nai»>iipnL xliar r ***ej»: amh\ imf 1 ~tt ini mm Y itWt 

• i/."- Til* *!'*** .^.'l-Ul*-— Ull'. » "X-*!! - 



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Chap. Vm. MONT MEZEN. 155 

immediately find ourselves surrounded by volcanic remains of a 
different character to those we left behind on the other side of 
the river, and evidently foreign to that focus of eruption. The 
Allier may, therefore, in a general way, be established as the 
natural boundary of the volcanic districts of the Cantal and 
Haute Loire. 

The volcanic remains of the departments of Haute Loire and 
Ardeche, or, in other words, of the ci-devant provinces the Velay 
and Vivarais, belong to both the classes which have been dis- 
tinguished above, and accordingly arrange themselves under these 
separate heads : — 

1. The Mont Mezen and its dependencies. 

2. The products of more recent eruptions, which have burst 
out on numerous points irregularly scattered over a broad band 
of the primary plateau, from Paulhaguet and Al&gre to Pradelle 
and Aubenas, seeming to be a prolongation in a S.E. direction of 
the chain of recent volcanos already described in the department 
of the Puy de Dome. 

§ 2. The Mont Mezen and its Dependencies. 
The Mont Mezen is the most elevated of an extensive system 
of volcanic rocks, resting partly on granite or gneiss, and in 
part on the Jurassic formation, which by their position and con- 
stitution prove themselves to be the remains of a single and 
powerful volcano, of the same character as those which have 
been already described in the Mont Dore and Cantal. Its 
products, however, are disposed in a somewhat different man- 
ner, being spread over an almost equally extensive surface 
without accumulating into such mountainous masses around 
their centre of eruption. Two causes seem to have contri- 
buted to occasion this diversity of aspect, namely : first, that 
the eruptions of this volcano appear to have been less frequent 



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156 VOLCANIC FORMATIONS OP THE VKLAT : Chip. VOL 

than in the other instances; secondly, that its forms consist 
either of basalt or clinkstone almost exclusxvelv, Terr little 
granular or common trachyte occurring among them. They, 
therefore, were probably possessed of great comparative fluidity ; 
and having burst out on one of the highest eminences of the 
primary platform, which afforded a considerable slope in most 
directions, they appear to hare flowed to great distances imme- 
diately upon their protrusion from the volcanic vent 

Owing to these circumstances the fundamental granite is dis- 
closed occasionally in ravines up to the foot of the central 
summits; and the highest of these, the Mont Mezen, though 
raised on a much more elevated basis than either the Cantal or 
Mont Pore, is inferior to both in absolute height It measures 
from the sea, according to Cordier, 5974 feet 

The Meaen itselC and the other principal masses grouped 
around it are almost uniformly composed of clinkstone (phono- 
litt\ scaly or schistose trachyte), a rock which ranks first amongst 
the products of this volcano; while the common or massive 
variety of trachyte is, if not totally absent, rarely to be met with 
through* vut the whole system. Basalt occurs in great abundance, 
and is asftviatcd mith vast beds of its peculiar conglomerates, 
analogous in their general characters to the same formation in 
the Mont IVw and Cantal, but owing to the non-production of 
traehjtie lavas, with little if any pumice in their composition, 
ami consequently alraos* always in the state of basaltic breccia 
lltasah tnflTV 

Wo shall he fully justified, by the universal declination of 
thoae ditVerent wJoanie bods from the Mont Mezen, in fixing the 
*ito tvf thoir eruption in its immediate proximity; and on the 
nouth-caM i>f this rocky eminences in the vicinity of the Croix des 
lloutt^iVN there still c\Kt$ a seniieiirular basin whose steep 
Milr* aiv cniuvh formed <if scoria* and loose masses of very 



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Chap. Vm. GREAT CLINKSTONE CURRENT. 157 

cellular and reddish-coloured clinkstone, and which probably 
therefore formed a part of the circuit of one of the last-formed 
craters. From this spot two principal embranchments of clink- 
stone are projected, one to the south, the other to the north-north- 
west 

The first shows itself in between twenty and thirty neighbour- 
ing rocky eminences of very considerable magnitude, and more 
or less degraded to a conoidal form, studding irregularly the high 
platform of the Haut Vivarais. From the foot of one of these, 
called Le Gerbier des Jones, gushes the source of the river 
Loire. 

The second constitutes a mountainous chain of numerous 
similar domes or cones, connected in general by their bases, and 
covering a wide band of country as far as the towns of Boche en 
Eegnier and Beauzac on the northern side of the Loire. The 
uniformly progressive declination of this series of phonolitic 
summits from the Mezen to the bed of the river, where they 
terminate, the two last, called Miaune and Gerbison, leaning 
against the foot of the primitive range of La Chaise Dieu on the 
opposite bank, leads to the impression that they are the remaining 
portions of a single enormous lava-current, prior in date to the 
excavation of the actual channel of the Loire, and far the most 
considerable in bulk and extent of any in the Phlegwean fields 
of France. The space it appears to have covered is more than 
twenty-six miles in length, with an average breadth of six, con- 
taining therefore a superficies of 156 square miles. Its thickness 
must have originally been prodigious, and may be judged of by the 
mountainous portions still remaining, whose outline is to be seen 
in the accompanying panoramic sketch.* Many of these rise to 
a height of 400 and 500 feet from their base ; and none, I be- 



* See Plate XI. 



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156 VOLCAKTC FOBMATTOSS OP THE VKLAT: Chap. Vm. 

lieve, show any marks of a division into separate beds ; so that 
the whole colossal range most be supposed one current, the 
product of a single eruption. It rests generally on granite, 
either immediately, or with the intervention of basalt and its 
conglomerates ; but appears also to have covered a large angle 
of the calcareous freshwater formation which we have already 
described as occurring in the neighbourhood of Le Pay. 

As the determination of this fact may be considered an object of 
some moment, I took some pains in its examination. At the Castle 
of Lardeyrolle, and on different points near the villages of St 
Pierre Eynac and MertXBur, the clinkstone certainly rests in part 
on the freshwater strata. Immediately below the latter village, 
which with the ruins of its castle is built on a conical peak of clink- 
stone, the superposition is decided and immediate. It is true that 
the nucleus of this and the other isolated hills capped by clink- 
stone which I observed within the limits of the freshwater forma- 
tion, is of granite ; and the great inclination of the calcareous 
strata of Mercosur, at the point where they support the clinkstone, 
indicates the granite against which they abut to be at no great 
distance. But it is not difficult to conceive that by this subjacent 
primitive nucleus alone the capping of clinkstone has been pre- 
served from destruction ; nor is it strange, a priori, that this 
rock should rarely be found resting solely on the calcareous strata, 
for the reason that the latter, consisting in this quarter of very 
soft and friable clays or marls, may be supposed to have every- 
where yielded to the erosion of the pluvial waters, to which the 
highly fissile structure of the superincumbent rock would give an 
easy access ; and owing to which, the whole of the clinkstone 
bed which covered these soft freshwater strata has probably been 
undermined, precipitated, and swept away ; with the exception 
of such portions as were accidentally based upon some granitic 
knoll protruding through the marls, as in the instances quoted. 



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Chap. VTIL CLINKSTONE OF MONT MEZEN. 159 

In fact, the most friable of the freshwater strata, the clays and 
marls, have generally disappeared; all but a few scattered 
patches which lean against the primary edges of their basin, or 
those portions that were protected by a coyer of basalt and its 
indurated breccia, which, being less permeable to water than the 
fissile clinkstone, have remained longer on their treacherous 
foundation : but even these are reduced to comparatively small 
segments of beds originally very extensive, and annually suffer 
more or less diminution by the sapping and mining of their 
base. 

Again, that the production of these volcanic rocks occurred 
subsequently to the deposition of probably the entire freshwater 
formation, is confirmed by a negative proof of the strongest 
nature, viz. the total absence of clinkstone fragments among its 
transported materials, or the sands and sandstones that under- 
lie it ; while, on the contrary, they abound in the alluvia and 
volcanic beds which were deposited upon these after they had 
been considerably degraded. It is scarcely possible that the 
bed of clinkstone could have been worn down to tjie insulated 
peaks now existing, before or during the deposition of the sands 
and marls, without a fragment or a pebble of it being found 
in these strata to attest its destruction. 

Many geologists have remarked the tendency of phonolitic 
mountains to waste into detached masses of a conical form. No- 
where could this observation be better appreciated than along 
the range I am now describing, which is entirely reduced to a 
series of rocky eminences, presenting every intermediate grada- 
tion of figure from the rude segment of a bulky hummock to a 
^perfect cone. 

The cause of this uniformity clearly lies in the much greater 
facility with which thip rock yields to meteoric influence on some 
points than on others, as well from its frequent differences of 



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K- ■>■■ „ " ^-w-iaaa. etc 

■ «,, ... X. * ^ "'■'* "*" —* <=?«* — = 

■ - - -, ,; LZT'T* **** m ^ *-* 

"- ' ' ' ^: ,.;£^^^«*-*: 

< ^ u ;,C', W »**-**»- 

'"«" huiMihH ut '* UUuL *W an eridcntJr , 



'/ 1 



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Chap. VIII. BASALT OF MONT MEZEN. 161 

more favourable circumstances would have united into distinct 
crystals. 

Small imbedded crystals of felspar are frequent, of augite or 
hornblende rarer. • The lower parts of the bed are somewhat 
porous and occasionally vesicular : in the vicinity of the central 
summits highly cellular and even scoriform masses are abundant ; 
they are usually of a reddish or reddish-blue colour, and a 
crystalline texture.* 

Basalts and Breccias. 

I have already noticed basalt as having been largely produced 
by this volcanic system. The currents principally flowed towards 
the north-west, west, north-east, and south-east, led by the supe- 
rior inclination of the primary platform in these directions. 

Towards the south-east in particular an immense embranch- 
ment, composed of two or more successive beds of basalt accom- 
panied by breccia, descends to a distance of more than thirty 
miles, rivalling in extent and volume that of clinkstone which 
we have described on the opposite side. 

This current is not less interesting from its position than the 
magnitude of its dimensions. It appears to take its rise from 
between the scattered peaks of clinkstone which have been 
noticed above as grouped together on the south of the Mezen, 
and is prolonged with a gentle slope towards the south-east for 



♦ I am aware that, in attributing the animation I was able to make confirmed 

chain of clinkstone hills which stretch me in my original opinion. And, more- 

from the Mezen to Miaune to a single over, I felt a strong suspicion that on 

colossal current worn by the elements many points of this range the clink- 

into fragments, I am differing from the stone hummocks rest upon basalt which 

greater number of local geologists, who had previously flowed as lava in that 

consider these domes or puys to be direction over the granitic surface. I 

each the product of a separate local would strongly recommend the investi- 

outburst. I can only say that, on my gation of these two questions to such 

recent visit to the district, all the ex- geologists as may visit this country. 



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IG2 VOLCANIC FORMATIONS OF THE VELAY: Chap. VIII. 

the space of about twelve miles, resting on the high primitive 
platform of the Haut Vivarais, and forming an elevated ridge 
which separates the waters of the rivers Ardeche and Erieux. 
Near the line of junction of the primary and secondary forma- 
tions it is broken off by a deep gap, through which passes the 
road from Aubenas to Privas. But on the opposite side of this 
depression the same bed is repeated at a precisely corresponding 
height on the summit of a mountain of Jura limestone. From 
hence it is continued with a similar gradual inclination to a 
direct distance of about twelve more miles. As long as this bed 
is based on granite its breadth is trifling, and it shows itself 
rather as a continuous flat-topped mountain-crest than in the 
usual form of a wide plateau. But on entering the limits of the 
secondary formation it assumes a different disposition, spreads 
itself to a width of five, seven, and nine miles, and covers an 
extensive and elevated table-land, which under the ancient 
regime went by the name of the Coiron. There cannot be the 
least doubt but that the whole of this lofty tract of Jurassic strata 
has l*een solely preserved from destruction by its volcanic capping. 
The remainder of the formation around has been eaten into 
in nil directions by various mountain torrents, and gnawed down 
by meteoric abrasion to a far lower level. The Coiron alone 
beneath the shelter of its basaltic coating has effectually resisted, 
and juts out like a huge flattened headland from the margin of 
the high primary plateau into the southern plain. It has not, 
however, escaped uninjured. The agents of waste, to which the 
iron hardness of basalt itself ultimately yields, have intersected 
it by numerous transverse ravines, excavated sometimes to a 
considerable depth through both the volcanic and calcareous 
strata. They are separated by massive parallel embranchments, 
which derive from a straight longitudinal axis, exactly in the 
manner of ribs from the spine. On either side there are as 



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OS 



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Chap. VIIF. THE COIRON. 163 

many as eight or nine of these, each crowned by a prodigious 
tabular load of volcanic products, presenting in its section a vast 
range of vertical cliffs resting on the secondary limestone strata. 
The perfect correspondence in position, structure, and dimensions, 
of these cappings, as well as their all branching off from the 
same stem, testify to their having been once united in a single 
continuous platform ; and in all their aspects, but particularly 
from the side of Villeneuve, where the extremities of six or seven 
of these ramifications may be taken in at once by the eye,* their 
appearance is striking in the extreme. 

The thickness of the volcanic mass is usually between 300 and 
400 feet, which appeared to be made up, wherever I examined 
it, of two enormous distinct beds of basalt, separated by a layer, 
varying greatly in thickness, of scoriae and volcanic fragments 
united into a breccia, or of loose scori© alone. Each bed, but 
particularly the inferior one, presents a sort of lower story of 
very perfect and well-matched vertical columns, surmounted by 
a still thicker mass, which is comparatively amorphous, but on a 
near approach is seen to consist of innumerable small columns 
both straight and curved, disposed in every possible direction 
and entangled into every variety of figure. These two por- 
tions are blended at their line of contact in such a manner 
that it is impossible to doubt their belonging to the same bed. 
The basalt of the uppermost surface is porous, slaggy, and scori- 
form.f 

The almost architectural symmetry resulting on many points 
from this arrangement was probably the origin of the fable 
current among the peasants of the plain below, who still call 



* See Plate XII. Also the General specie the very recent lava-streams of 
Map of Central France. the Vivarais to be described in a sub- 

f Exactly resembling in these re- sequent page. 

M 2 



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r THF TELAT : Chap. VHI. 
*" xii: imagine them to hare 

zi-n^ -:~5iwsi«fing in age to 

- z. i^rv i-fcVfy and friable, 

^-^* xi-^ cs^eqnently yields 

. «^i - - i5- are tiras ire* 

- .— : ->* -r^ifc ..^ir themselves, 

of the cal- 

-c with their 

=ib-*^ •■ _**c c parcel* of 

.=_-.>. :*r -*c~ rf Roche- 

*-".*- ■*»■ ■u. , »^5 in its 

_^*r*- *- zr -c ti*w arms 

. -- r* = ^r*t:ies out 

- - =r i- r t. he in 

^- » t -v * a <n -r gri b a 

. * -•/ * * iL^pHtaf 

xh~ -x ^ni*caacii- 

** -^^^ r * ar«rOi«i 

.- . * n^r * fc«h 



—^ av iCItrffS 






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Chap. VIII. THE COIRON. 166 

proceeded from an overlying mass of basalt now destroyed, the 
prolongation of that above St. Jean. The enormous fragments 
which still strew the valleys of the Laduegne and Escoutay are 
sufficient to prove that the bed did not originally terminate at 
its present limits in that direction. 

The ravine called Les Balmes de Montbrul, which M. Faujas 
considered to be a volcanic crater, is merely an accidental 
excavation, I believe, in the basalt and scoriaceous breccias of 
this bed. 

On the whole there are many circumstances, besides their 
immense bulk, attending the basaltic currents which cap the 
Coiron, that render them in a geological light perhaps the most 
instructive of any in the interior of France. Their disposition 
at first in a narrow ridge across the granitic heights, then in a 
widely-spreading sheet over the secondary formation, perfectly 
parallel to its strata, and everywhere preserving the same gradual 
declination from the neighbourhood of the Mezen to the extre- 
mity of the Coiron, evidently demonstrates their having flowed 
at an epoch when the surface of the primary platform was 
directly continued in that of the secondary strata ; and appears 
to indicate that this last formation at least was at the time in a 
state of comparative integrity. 

That it had, however, long emerged from the ocean in which 
it was deposited, is attested by the circumstance that beneath 
the basalt a vegetable soil is found containing terrestrial shells 
of a species still existing in the same country (cyclostoma 
elegans). 

The immense quantity of matter which must have been ab- 
stracted from the secondary district of the Kh&ne valley since the 
epoch at which this lava was emitted — an epoch which this last- 
mentioned fact proves to be but recent (geologically speaking) — 
cannot but strike us with astonishment. There can be no doubt 



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166 VOLCANIC FORMATIONS OF THE VELAY : Chap. VIII. 

that the surface on which the basalt of the Coiron rests was at that 
period the lowest of the neighbouring levels, or these repeated cur- 
rents of liquid matter could not have flowed in its direction ; yet at 
present this same surface vastly overtops every other height of the 
same formation, and ranges upwards of a thousand feet above the 
average level of the valley-basins of the Ardfeche and Rhone on 
either side. That a considerable proportion of these was exca- 
vated by "rain and rivers," in other words, by meteoric agency 
such as is still in operation, and not by any diluvial or general 
flood, is susceptible of direct proof, as will shortly appear from 
bur examination of the volcanic formations of the Bas V ivarais. 
To attribute, therefore, the remainder to any other cause of an 
hypothetical nature unsupported by evidence, would seem to be 
contrary to the rules of analogy. But the conclusion that the 
greater portion of the valley of the Bh6ne has been so recently 
excavated, and by such agency alone, involves important conse- 
quences ; since the same agents must have been at work every- 
where else, and produced results as stupendous during the same 
(comparatively) recent period. These considerations will be 
resumed hereafter. 

I now proceed to the other basaltic remains which owe their 
origin to the volcano of the Mezen. They form the covering of 
a very extended surface ot the Haut Vivarais and Velay, but, 
from their situation on so elevated and exposed a region, have 
been intersected in all directions by the channels of mountain 
torrents, so as to disclose the subjacent rock, which is every- 
where granite, except within the boundaries of the freshwater 
formation of Le Puy. 

It is remarkable that detached plateaux of basalt are scattered 
profusely near the borders of the great phonolitic embranchments 
noticed above. Not unfrequently the interval between two or 
more conoidal rocks of clinkstone is occupied by a flat superficial 



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Chap. VIII. BASALTS OF MONT MEZEN. 167 

bed of basalt extending quite up to their bases ; and it is very 
difficult, in consequence of the excessive degradation of the 
clinkstone and the piles of debris which gather round their skirts, 
to ascertain whether the basalt passes below them, or has been 
deposited since their separation. The former conclusion is, 
perhaps, the most probable. 

The basaltic beds which flowed eastward from the Mezen reach 
from Fay le Froid to beyond Saint Agr&ve ; constituting the crest 
which separates the waters of the Loire from those that flow into 
the Rhone. On many points they have been reduced to scattered 
patches by the same causes which have cut up and ravined to a 
great depth that barren and dreary primary canton called Les 
Bouttiferes. Those which took their course to the north and north- 
west are more entire, descending into and traversing the valley of 
the Loire, accompanied by large accumulations of conglomerate. 
I think it probable that the basin of the freshwater formation at the 
period of its invasion by these volcanic products had been laid dry, 
and was even partially eaten into by the torrents that descended 
from the environing heights : that the position of the river which 
then effected its drainage and received these streams was much 
to the west of the actual channel of the Loire, and at the foot 
of the western granite range : and that in this state of things 
the whole of the basin up to that range was deluged by vast 
currents of basalt, which flowed from the vicinity of the Mezen 
in company with an immense quantity of fragmentary materials, 
transported by torrents of water and deposited in the same dis- 
order as the conglomerates of the Cantal and Mont Dore. 

The facts on which this opinion is built are contained in the 
following observations, which will be made much clearer by the 
accompanying panoramic sketch of this district* 



* So* Plate XI. 



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168 VOLCANIC FORMATIONS OF THE VELAY: Chap. VIII. 

From the centre of the volcanic system near the Mont Mezen 
vast beds of basalt are seen to stretch with a gradual inclination 
over a wide surface of granite, towards the west and north. On 
attaining the freshwater formation they are prolonged over it 
exactly in the same manner, without any material change in the 
angle of their slope and few complete interruptions to their con- 
tinuity. Where these do occur, the original union of the different 
segments is evident from the corresponding altitude, disposition, 
and nature of the masses which border either side of the valley. 
In this way they extend to a considerable distance beyond Le 
Puy ; and though towards the extremity of their course they have 
been themselves covered by more recent and scarcely less copious 
lava-streams from a different source, they may still be universally 
recognised by their peculiar characters, along the mural flanks 
of the numerous ravines which intersect this plain, almost up to 
the base of the western granite range. 

While describing the freshwater formation of Le Puy, I spoke of 
it as arranged in strata having a progressively decreasing dip from 
the granite against which they lean. It is remarkable that the 
volcanic beds are not parallel to the planes of these strata by which 
they are supported, but cut across them irregularly, and often 
very abruptly ; as for example in the Montagne de Doue, where 
the dip of the clays and marls is scarcely 10°, while that of the 
superposed bed of basalt and breccia is in some parts 40° and 50°. 

Nor do the volcanic beds in general rest immediately on the 
calcareous strata, but with the intervention of a layer of clayey 
and micaceous sand mixed with volcanic ashes, and the debris of 
granitic and volcanic rocks, particularly rolled fragments of clink- 
stone. This stratum is not parallel to those of the freshwater 
formation on which it rests, but to the volcanic beds by which it is 
covered, and was evidently deposited in channels already deeply 
excavated through the soft calcareous strata below. It generally 



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Chap. VIII. BASALTS OF MONT MEZEN. 169 

encloses vegetable remains, slightly carbonized, and on certain 
points so abundant that this alluvium passes into a lignite, of which 
some beds are occasionally of sufficient thickness to become the 
object of extraction, ad at Aubepin and La-roche-lambert The 
plants are either reeds and grasses, or leaves, twigs, and branches, 
of dicotyledonous trees. M. Aymard pronounces the opinion, 
that the Flora of this alluvium is scarcely, if at all, distinguish- 
able from that still existing in the district. The Fauna of the 
same beds (which are very ossiferous), on the other hand, con- 
tains many species not only unknown in France, but altogether 
extinct ; especially is this the case with the mammiferous ani- 
mals, among which are found here the remains of three species 
of mastodon, several carnivora — machairodus, hyaena, &c. ; of 
Pachyderms, a rhinoceros (Mesotropus, Aym.), and a tapir, &c. 
(See the catalogue subjoined in Appendix.) 

Where this intermediate layer of alluvium is absent, and the 
volcanic products rest directly on the freshwater strata, the line 
of contact exhibits a breccia of scoriae and puzzolana enclosed in 
a calcareous or argillaceous paste, .such as has been remarked in 
parallel situations in Auvergne. In some cases this breccia 
appears to proceed in part from decomposition of the volcanic 
beds above, and tf ould be classed mineralogically as a wacke. 
It is remarkable beneath the mass of basaltic breccia called 
Les Rochers de Peylenc, for containing numerous nodular 
blocks of olivine of an extraordinary size. One of an oval 
shape which I measured was five feet in circumference, many 
others around were nearly as large. These masses are 
rounded as if from bouldering; yet those which are em- 
bedded in the basalt above have the same figure ; * they break 



* They have, I conceive, been rounded in a state of imperfect liquidity. See 
by the internal friction of the lava which Scrope on Volcano*, p. 104. 
enclosed them, as it flowed onwards 



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'^-' - T TEr TELAY: Chaf. VHI. 

-=" ~=— * jdl » of i transparent 

*-- ^-. rr^r « darker green when 

«» x wij:i iiik prooeaB has 

— ake. jac •£ a dnD yellow or 




•^ * ^ . ^ -- • -*.-*- >Tui^i. jar i*s often a ten- 

* . .--- -..^r.-.: i. > .» :£*&> <t*<h angular 

* -^ - > . 'w. ■* • is> . iLfci* sjteisw of granite, 

. - . . *nv >^ *** •,- **s* z—1*- i aurfr limestone ; 

.^ „ ^« -• .. .sv-.^ T":r ^flternt fc ^neralhr 

^ . ^->v ;^*- -,-* ■ »-•.« r i*i I presrav* putkipafang 

- -. ■ -■ o- -1.--P- i r>. : rair r^£> and passing 

o ik""js ». %- •— :i £» c-ra* »f* tie rucks whooe 

>* .... :;n* ^ «». c*'i«* t meivlY an oxide 



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Chap. VIII. BASALTS OF MONT MEZEN. 171 

of iron, at others basalt itself fills the interstices of the broken 
materials, appearing to have enveloped them in a state of 
fluidity. 

The basalt varies in character in different parts, seeming to 
belong to separate currents. It is, however, generally columnar ; 
often presenting the greatest accuracy of design, as in the rock 
behind the mansion of Done, and on numerous other spots along 
the valleys of the Loire and its feeders. On more than one I have 
observed the three chief modifications of divisionary structure — 
the columnar, tabular, and spheroidal — distinctly exemplified in 
the different parts of the same mass, and passing into one another. 
Its mineralogical characters are extremely diversified. Some- 
times as we have seen, imbedded knots of olivine predominate, 
sometimes crystals of augite, of hornblende, or of glassy felspar. 
Many varieties are much iron-shot, and then black, compact, 
hard, and sonorous; others have almost an earthy feel, the 
colour of a dead leaf spotted with bluish-grey, are porous, and 
decompose rapidly, separating into angular globules. Such is 
that which occurs on each side of a small ravine running up 
from the village of Expailly, near Le Puy, to the foot of a hill 
called Le Mont Crousteix, and which contains the far-famed 
zircons, sapphires, and garnets of Expailly. They have been 
for many centuries found in the sand of the streamlet called 
Bioupezzouliou, that drains this ravine ; but it is only of late 
that they have been detected in their matrix, which is the 
above-described basalt The zircons occur in small imperfect 
crystals, and are collected in such numbers that I have seen a 
large drawer full. The sapphires are next in abundance, and 
are found in hexahedral prisms rarely exceeding three lines in 
diameter. The garnets are scarce, and in rhomboidal dodeca- 
hedrons, usually about the size of a large pea. But all these 
crystals, not only when taken from the alluvium of the ravine, 



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172 VOLCANIC FORMATIONS OF THE VELAY: Chap. V HI. 

but those also which are imbedded in the compact basalt, have 
lost the sharpness of their angles, and are in general much 
defaced There is, indeed, every reason, from their aspect and 
mode of setting, to suppose that their crystallization was not 
contemporaneous with that of the felspar, angite, and olivine 
which they accompany, but preceded it, and that these minerals 
resisted the fusion to which their original matrix was probably 
subjected before its conversion into a basaltic lava. 

Both basalt and breccia occasionally envelop irregular deposits 
of volcanic ashes having the appearance of desiccated day ; and 
this substance, where in contact with the basalt, is divided to 
the depth of about a foot into very regular columnar prisms, 
perpendicular to the surface of the basalt with which it is in 
contact, and whose most general mode of structure it accurately 
imitates in miniature. It is often of a fine texture, and a rich 
salmon colour ; sometimes graduates into a micaceous sand, the 
detritus of volcanic and primitive rocks, similar to that which 
occasionally forms the paste of the basaltic breccia, and on 
other poiuts into a conglomerate of bouldered pebbles. 

The valleys worn through this vast volcanic bed, and the 
lacustrine strata beneath it, offer here, as in the CantaL, an 
extraordinary series of pictures. The breccia, where it is much 
impregnated with iron, or otherwise considerably indurated, has 
rwi*tcd the agents of evusiou, and remains in isolated masses of 
grotesque forms* Such is tin? Rocher de Polignac, that called 
L'«jn*rilie, whose otdctuvous bae* is half encircled by the town of 
L* Puy. and that of Si. Michel* * needle-shaped and picturesque 
pyramid. cro*uc*l by a church, of which a tolerable engraving 
i* ^iv^n bv Faui*$ dc Si. FotaL* 






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Chap. VIII. BASALTIC DYKES. 173 

In frequent instances veins or dykes of basalt penetrate the 
subjacent strata, whether these are breccia, limestone, or granite. 
Examples of the first kind are exceedingly common ; one of the 
second may be observed at the foot of the hill called Brunelet, 
on the left of the road from Le Puy to Issingeaux. The dyke 
proceeds from a mass of basalt, and cuts vertically through strata 
of marly limestone. Its lower termination is not visible. The 
road from Le Puy to Bozi&res, on the descent towards Mercoeur, 
is traversed by a dyke of basalt about a foot and a half wide, 
and which can be traced only about seven or eight yards in 
length. It occurs exactly where the marly strata lean against 
the granite, and appears parallel to the plane of their junction, 
which is elevated at an angle of about 60 degrees from the 
horizon. One wall is unaltered granite, the other a narrow 
stripe of granite bleached and disintegrated to the state of gravel, 
intervening between the basalt and the calcareous strata. The 
basalt is accompanied by scoriaceous portions, and from its simi- 
larity of texture, and other mineralogical characters, as well as 
its position, appears to have derived from a conical mass still 
capping the granite at a higher elevation. 

The side of a narrow ravine at a spot called Les Pandreaux, 
between Lantriac and Le Puy, presented to view another nearly 
vertical basaltic dyke 3 feet wide, cutting through granite, 
which is considerably altered along the line of contact ; and at 
no great distance, in the same valley, rises the Koche Rouge. 
This is a swelling portion, or " renflement," of a basaltic dyke, 
which, from its hardness of substance and solidity of structure, 



'• Pyramids of Botzen " in the Tyrol, conglomerate bed of which these and 

each of which evidently owes its pre- similar pyramidal remnants formed a 

serration to a large boulder which caps part was effected solely by the force of 

its apex; whence it follows that the direct vertical rain. See note to p. Iu6. 
amount of excavation produced in the 



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172 

but 

lost 

m<> 

an. 
wl 

si 



A 



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Chap. VIII. CHAIN OF RECENT VOLCANOS. 175 

the condition which every ordinary volcanic vent productive of 
but a single minor eruption of basaltic lava would exhibit, when 
stripped of the outward coverings of scoriae and other fragments 
that in almost all cases conceal the orifice in the superficial 
rocks through which these matters were protruded. There 
appeared to me to be a separate axis of basalt penetrating the 
heart of the Roche Rouge, as if the lava had continued to be 
expelled through a central channel, after the external parts 
which were in contact with the granite had been consolidated to 
a considerable depth. The rock of St. Michel seems to contain 
a similar dyke, which may probably have been erupted on this 
spot. It is, however, of course evident that the conglomerate of 
which it is composed must have been originally enveloped and 
supported by surrounding beds of softer materials, since worn away 
by aqueous erosion, and the same is true of the Rocher Corneille, 
that of Polignac, &c. The existing valley of the Borne, as well 
as that of the Loire into which it opens, must have been exca- 
vated subsequently to the production of these remarkable rocks, 
whatever may be their date. On this point, however, the 
extreme similarity of these basaltic breccias to those of the 
Cantal attests their parallel origin. Though therefore the dykes 
by which they are occasionally penetrated may be considered 
the result of local eruptions, 1 cannot doubt that the breccias 
(of Corneille, &c.) are derived chiefly from the Mezen. 



§ 3. The Products op more recent and scattered 
Eruptions. 

We now come to the volcanic remains of the second class 
occurring within the departments Haute Loire and Ardeche. 
These are the products of a later epoch of volcanic activity, and 
almost uninterruptedly cover a broad zone of the primary 



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176 CHAIN OF RECENT VOLCANOS Chap. VITI. 

platform from a point north of Paulhaguet to Pradelle and 
Aubenas in the south. They constitute a prolongation of the 
chain of puys of Auvergne, but do not appear in any instance 
of quite so recent a date as the latest of those. 

The various points on which these eruptions hare broken forth 
are still marked by numerous volcanic cones of scoriae, whose 
projection, as in Auvergne, accompanied the development of the 
volcanic phenomena. They are so thickly sown along the axis 
of the granitic range that separates the Loire and Allier from 
Paulhaguet to Pradelle, as generally to touch each other by their 
bases, and form an almost continuous chain. 

On both sides of this they are more sparingly distributed, 
dotting here and there the slope towards either river ; a few being 
also found on the further side of each. Between Pradelle and 
Aubenas they occur more rarely, and none to the south of the 
latter town. There is, however, a large and productive group 
to the north-east of Pradelles, in the vicinity of Prezailles. 
Throughout the above-mentioned tract I counted more than 
a hundred and fifty of these cones, and probably omitted 
many. 

They are not altogether in the same state of freshness and pre- 
servation as the great proportion of those we have noticed in 
Auvergne. Not many present an entire or even a distinctly 
marked crater, and the generality have wasted to ridgy saddle- 
shaped hills, a form which volcanic cones have frequently been 
observed to assume by degradation. As usual, they are solely 
composed of slaggy and funiform scoriae, lava-bombs, lapillo, 
volcanic sand, fragments of granite and basalt, and sometimes 
massive portions of this last rock in *#u, the relics of the currents 
which descended their flanks or boiled up within their craters 
from the vent beneath. Their surfaces are scantily clothed with 
a meagre herbage, and occasionally a few stunted Scotch firs ; 



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Gbap.VIIL IN THE VELAY AND VIVARAIS. 177 

but their, dilapidation is incessantly going forward by means of 
frequent and shifting surface-rents. 

The lava-currents, whose emission accompanied the formation 
of the cones of the principal chain, must have been exceedingly 
abundant According to the position of each point of eruption 
with respect to the slopes of the granite range, they appear to 
have directed themselves either to the east or west, descending 
into the bed of the Loire on one side and of the Allier on the 
other. The former have covered nearly the whole eastern slope 
of the range (the. granite which forms its nucleus appearing only 
at distant intervals or in ravines worn through the basaltic beds), 
and are continued over the freshwater strata in a uniform sheet, 
forming a very extensive and but slightly inclined tract, which 
they seem to have completely deluged. There is every indica- 
tion that, by these prodigious and perhaps nearly simultaneous 
irruptions of lava upon the basin of the Loire, the river was driven 
from its former bed and forced back upon the slope formed by 
the similar products of the Mont Mezen. It probably long erred 
between the two, every fresh invasion partially shifting and rais- 
ing the level of its channel, so that its actual valley, and those 
of its tributaries (especially of the Borne), are excavated as 
well through the vast mass of earlier basalt and breccia, which 
we have seen chiefly proceeded from the habitual vent of the 
Mezen, as through an uppermost bed, generally single, of basalt 
alone, which, in its fresher aspect and uniform inclination from 
the chain of volcanic cones, is proved to derive from them. These 
later lavas are separated usually from one another, when re- 
peated, and also from the older basalts and breccias when they 
overlie the latter, by beds of conglomerate containing scoriae* 
fragments of granite, &c., and often layers of bouldered pebbles, 
showing the currents to have occupied, as usual, the shifting 
beds of the rivers and mountain torrents. Where the frag- 
mentary matter has been taken up and deposited by these torrents, 

N 



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178 CHAIN OP RECENT VOLCANOS Chap. YHL 

breccias have been produced identical with those of an earlier 
epoch.* 

These changes in the position of the Loire seem to have been 
accompanied by the progressive excavation of that deep and 
narrow golly through which this river now escapes from the 
basin of the freshwater formation of Le Puy,t and which could 
not have existed at the period of the flowing of certain beds of 
basalt (the plateaux of Chambeyrac and l'Onlette) that are seen 
capping its perpendicular cliffs ; or it must have been completely 
choked up by the lava to the level of these plateaux, like 
the valleys of the Bas Vivarais, which we shall shortly have to 
notice. This channel has been worn irregularly across the high 
granitic embranchment of Chaspinhac which separates the basin 
of Le Puy from that of Emblavte (a minor division of the same 
freshwater formation), and may perhaps have been partly occa- 
sioned by the creation of a fissure in that direction through some 
earthquake attendant on the volcanic eruptions. It is even pro- 
bable that the waters of the lake were previously discharged by 
another outlet, perhaps over the low part of the granite ridge 
between Blaves and St Etienne. 

Between these two points may be seen another striking proof 
of the vast amount of erosion effected by the existing torrents, in 
the gorge of the Sum&ne, a stream which joins the Loire just 
before it enters the defile at Pierre Neyre. On the left of this 
deep hollow the basaltic plateau called Chauds de Fay rests 
upon tertiary strata. On the right, the cone of sconce called 
Mont Serre is perched upon the edge of the granitic escarpment 



* M. Aymard (from whom I differ these numerous cones to have produced 
with great deference to his superior no lava-streams! This would be so con- 
local knowledge) is of opinion that these trary to all analogy, not only of the 
basaltic beds belong to a period much Auvergne and Vivarais north and south 
earlier than the volcanic cones of of the Velay chain, but also of volcanic 
scoria) which they surround. So far as phenomena in general, that I cannot 
I understand his views, he appears to for a moment asaent to its possibility, 
suppose the eruptions which threw up f See Plate XI. 



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CttAP. Vm. IN THE VELAY AND VIVARAIS. 179 

of Chaspinhac. And yet the position and inclination of the 
basalt of Fay proves it beyond all doubt to have flowed as a 
lava-stream from this vent across the space now occupied by the 
deep channel of the Sumfene, which could only have been ex- 
cavated by its existing stream (aided, perhaps, by some earth- 
quake fissure), since the entire condition of the cone of loose 
scoria above rebuts the supposition that any general denuding 
wave can have passed over these heights since its production. 

After traversing the lower basin of Emblav&s the Loire finally 
issues through another similar defile, where its passage seems 
once to have been effectually barred by the great current of 
clinkstone already described, of which two colossal remnants, the 
rocks Miaune and Gerbison, rising on either side the gorge to a 
height of 1800 feet above the river, attest the original elevation. 
That this enormous dyke suddenly thrown across the valley of 
the Loire must have caused its waters to accumulate into a lake 
covering the whole extent of the freshwater formation, is ex- 
tremely probable. It is not, however, to this event we can 
attribute the original creation of the lake in which the freshwater 
strata were deposited ; for the granite which supports the bases 
both of Gerbison and Miaune at a height of 1100 feet above the 
present river would alone have formed a sufficient barrier for 
that purpose ; and we have also seen that there is reason to con- 
clude the clinkstone more recent than the freshwater formation. 
The gradual erosion then of the gorge of Chamaliire, through 
both the mass of clinkstone and the granite on which it rested, 
was probably coeval with that of the channel of discharge of the 
upper basin ; and some remnants of basalt which show themselves 
attached to the sides of the excavation at Pierre-neyre and Artias 
prove the former to have been occupied at intervals during this 
process by lava-currents from the neighbouring vents of eruption. 
Among the puys of the Monte Dome we are enabled by their 
comparatively rare occurrence, and the intervals of primary rock 

N 2 



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180 



CHAIN OF RECENT VOLCANOS. 



GKAK.T1IL 



which separate their products, to trace almost every stream of 
lava to the crater which marks the spot of its emmaon ; but in 
tills chain of vents the cones are more numerous and doeex, the 
volcanic energy seems to have been exerted far more finioadyv 
and the lava-currents to have united into one contmnous and 
enormous crust, where all are mingled and confounded.* An 
extensive and gently sloping plain has thus been created, appear- 
ing thinly dotted by the cones which have been thrown up to the 
east of the principal line. Each of these has in all probability 
furnished its contingent to the sea of basalt that overspreads the 
plain ; but all attempt at appropriation is out of the question. 
A few show themselves in the vicinity of Le Puy, having burst 
through the great volcanic bed which, descending from the 
Mozen, had previously invaded the basin of the freshwater forma- 
tion. Such are the Montagnes de Denise, Ste. Anne, Seinzelles, 
Crousteix, Eysenac, and Mont In their scoriae are implanted 
numerous fragments of granite and gneiss: which prove that 
the source of their eruptions was more deeply seated than the 
breccias and basalts through which they burst To one of these 
eruptions, and probably to that which produced the double hill 
of Mont, south-east of Le Puy, is owing a small platform of 



♦ I Again refer to the parallel Instance 
of the chain of volcanic cones thrown 
up in the Uland of Lanoerote, one of 
the Canary Isles, by the tremendous 
voloanio eruptions to which that island 
was subjected betweon the years 1730 
and 17M. (See p. 95, above.) A very 
interesting description of these volcanic 
products, accompanied by a relation of 
the principal occurrences of the eruption, 
from a M8. narrative written by an eye- 
wltue**, haa been published by M. de 
lluch. The formation of 30 distinct 
tH>u«M on a Assure of great length, within 
ho abort a space of time, leads to the 
Nupposltion that many of the eruptions 
which threw up the puys of Auvergnc 



and the Velay were similarly 
stanced. Not that the whole chain 
was contemporaneously produced, for 
this is opposed to the numerous ap- 
pearances of unequal antiquity already 
dwelt upon at length in their descrip- 
tion, particularly with respect to those 
of the Moots Dome; but that epochs of 
intense activity altercating, as is the 
usual character of volcanic action, with 
lengthened periods of quiescence, fre- 
quently gave birth to a great many erup- 
tions from independent vents within a 
short space of time, creating as many 
distinct cones, arranged either in lines 
or groups, and as many streams of lava. 



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Chap. VUI. HUMAN B0NE8 IN BRECCIA. lfcl 

columnar basalt called Montredon, rising in the middle of the 
valley of the Borne, and resting on a shingle of primary and 
volcanic boulders, evidently at one time the bed of the river, 
though now more than 50 feet above its present channel. This 
seems to have been one of the most recent eruptions of the 
district And it is remarkable that in no instance are lava- 
streams found, as in Auvergne, occupying the river-channels of 
the existing valleys, as if they had flowed but yesterday. 

The cone that has attracted most observation, owing to its 
immediate vicinity to the town of Le Fuy, is that of the 
Montagne de Denise. And it does, in fact, offer some peculiar 
features of an interesting and problematical character. The 
summit and flanks of this oblong hill are covered with large 
accumulations of very fresh-looking scoriae, lapillo, and puzzolana, 
out of which several prominent masses of basalt are projected 
into the valleys around and beneath. One of these forms a 
bulky promontory, descending to the level of the river Borne on 
the south, and exhibiting two colossal ranges of basaltic columns, 
one above the other : the upper is called the Croix de la Paille, 
the lower (which hangs in a cliff over the river) the Orgues 
d'Expailly. At its sides and base this basaltic mass is enveloped 
and passes into a stratified and sometimes laminated breccia 
or tuff of no great coherence which clothes some of the outer 
slopes of the hill. Other massive rocks of a breccia or peperino 
similar to that of the Bocher Corneille in the town of Le Puy, 
constitute the nucleus of the hill itself, and through these the 
eruption of the more recent lavas and scoriae evidently broke 
out This massive and indurated peperino is of much earlier for- 
mation than that which accompanies the erupted lavas and scoria^ 
although the two breccias can with difficulty be distinguished, 
and in places appear almost to graduate into each other. There 
would be little remarkable in this were it not that in the last- 
mentioned stratified deposits large quantities of bones are found of 



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182 



CHAIN OF RECENT VOLCANOS 



Chap. VIE. 



elephant, rhinoceros, Cervns elaphas, and other large mammifere, 
and in one locality the undoubted remains of at least two human 
skeletons. A block of this breccia containing the greater portion 
of a human skull and several other bones is preserved in the 
museum of Le Puy. The matrix in which these fragments are 
firmly embedded is unquestionably a portion of a stratum of 
indurated tuff or breccia which envelops and passes into the 
basaltic lava of Denise. The examination I made on the spot, 
which is just above a house called the Hermitage on the road 
from Le Puy to Brioude, left no possible doubt of this fact 
on my mind. It was discovered in 1844, and the attendant 




Moot Denlae, near Le Pay. from the Sooth- We*. 




10. 



Moot Denise, near Le Pay. from the Sooth-East. 



1. Old Breccia Rocks of the CoL 

2. lload from Le Pay to Brioode. 

3. Croix de la Faille. 

4. Orgoes d'Expailly. 



6. (In lower cat) Spot where human bone* 
were found in strata of toll 

5. (In upper cat) Spot where bone» of 
rhinoceros, elephant, fcc, abound. 

6 Castle of PoUgnac in distance. 



\ 



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Chap. VIII. IN THE VBLAY AND VIVARAI8. 183 

circumstances were carefully inquired into and reported to the 
Academical Society of Le Puy by M. Aymard. At the meeting 
of the Scientific Congress of France which took place at Le Puy 
in 1856, the question of the genuineness of this specimen was 
discussed, but no reasonable doubts could be thrown upon it, 
and the great majority of the savans who examined the question 
were of that opinion.* Nor, in truth, need there be any surprise 
at the discovery that this district Was inhabited by man at the 
period when the most recent volcanos were in eruption. The 
more remarkable inference from the discovery of these bones is 
that man had for his contemporaries in this country several 
races of extinct mammalia, of the genera rhinoceros, elephant, 
&c., whose remains are found in the similar stratified breccias 
occupying the same position on the slopes of the same volcanic 
cone. It is also evident that vast changes must have taken 
place in the configuration of the country since the eruption 
of the volcanic vent of Denise, and consequently since its 
occupation by man. The valley of the Borne must have 
been greatly widened and deepened, if not entirely excavated, 
since that epoch, and the time required for these changes 
throws back the date of the eruptions which buried in its 
ejections Hie two human 'skeletons of Denise to a very distant 
period. On the other hand, it is evident to any one who 
examines these valleys which drain the basin of Le Puy within 
the limits of the freshwater beds that the progress of denuda- 
tion is exceedingly rapid. The red and blue clays, gypseous 
marls, and flaky calcareous shales are readily undermined by 
the torrents which, however small in summer, in winter descend 
with great violence in this high region, and their debris are at 
once carried off in the shape of mud. Even the load of volcanic 
rock which is precipitated as the underlying strata give way 



* Congrta Scientifique, &c, 1856, voL i. p. 2&1. 



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184 CHAIN OF RECENT VOLCANOS Chap. ¥HL 

is soon reduced to pebbles and burned off. In the VivaraiB we 
shall have occasion to observe this process going on very obviously, 
and in a manner strikingly suggestive of the prodigious results 
it is calculated to effect within no very great lapse of time. 

In the majority of instances, as near Chaspinhac, St Geneys, 
Couron, Al&gre, &a, the cones rise immediately from granite* 
That in the neighbourhood of the last town, called La Mcmtagm* 
de Bar, has a large and regular crater at its summit, about a 
mile in circumference and 150 feet in depth. A flat area 
700 feet in diameter occurs at the bottom, which once contained 
a small lake or pool of water, but has been artificially drained 
by a channel cut through the lowest part of the encircling ridge. 

The lava-streams which descended from the principal range of 
cones towards the Allier have in a similar manner encrusted the 
western slope with a thick coating of basalt, and appear to hare 
occupied the former bed of the river nearly in its whole extent 
from Langogne to Vieille Brioude. The primitive chain of La 
Marg&ride, however, rising immediately from the western banks 
of the Allier, drove the river back upon the basalt that had 
usurped its channel, and through this, as well as the granite 
beneath, it has excavated afresh one. By this process have been 
disclosed many most magnificent mural ranges of columnar 
basalt which at St Ilpize, Chiliac, St Ar^on, Monistrol, &c, 
encase and frown over the river. They are generally seen to rest 
upon a bed of water-worn pebbles, from 100 to 150 feet above 
the present stream, and may be traced eastwards uninterruptedly 
to the volcanic cones on the slope or summit of the range above. 

The'basalt originating in this linear group of volcanic mouths 
assumes on different points a very regularly columnar, a tabular, 
and a spheroidal concretionary structure. It sometimes also 
separates so readily and to such a degree into small angular 
globules from the size of a nut to that of a millet-seed, that the 
roads are strewed with them to the depth of some inches, and 



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Chap. VHI. IN THE VELAY AND VIVARAlS. 185 

the foot often sinks into rocks of this nature as into a heap 
of gravel. In mineralogical characters the rock varies from 
distance to distance. Among the remarkable kinds I noticed 
one with very large spherical cells and an exceedingly crystalline 
texture ; the interlaced grains being felspar, augite, and a bright 
yellow transparent olivine. It occurs round La Eoche on the 
load from Le Puy to St Privat; another, near St George 
d'Aurat, dense, heavy, and iron-shot, contains still larger oblong 
cavities frequently coated internally with fiorite. 

In this range also, as in the Monts D6me and Mont Dore, 
we meet with a few lakes occupying wide, deep, and nearly 
circular basins, which bear every appearance of having resulted 
from some violent volcanic explosions, but differ from ordinary 
craters, not only in their greater dimensions, but in the nature 
also and disposition of their enclosure, which is usually of primary, 
or, at all events, pre-existing rocks, merely sprinkled more or 
less copiously with scori© and puzzolana, little if at all elevated 
above the surface of the environing country. Such are the lakes 
du Bouchet, de Limandre, d'Issarles, de St Front, as well as a 
large and remarkable hollow, now drained, in which the river 
Fontaulier takes its rise, and which is traversed by the road 
from Usclades to Montpezat The latter crater contains a small 
parasitic cone rising from its bottom. I need not repeat here 
the remarks upon the peculiar modification of the volcanic 
phenomena to which this variety of crater apparently owes its 
formation, which were sufficiently dwelt on in the description of 
the Gour de Tazana.* 

Between Pradelle and Aubenas the cones diminish in number, 
rising here and there through the great forest of Bauzon, and 
showing themselves up to the escarpment of the elevated platform 
of the Haut Yivarais. 



• P. 81. 



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186 RECENT VOLCANOS IN THE VIVARAIS. Gu* VHL 



But the most remarkable and interesting by far of the 
volcanic remains of the zone we are now considering, and puhaf 
of all France, are those that occur on the steep declivity bw 
which this escarpment is connected with the great southern valley 
chp low-lands of the Bas Yivarais and Languedoc. 

I have already described the primary table-land as abrapdy 
cut down on this side. Its rapid slope is intersected by deep 
mountain gorges, into which frequently open the transverse 
trough-shaped valleys of the coal formation. Viewed from below, 
this front of the great platform appears as a precipitous curtain- 
like range, broken by recesses into short, steep, and massive pro- 
montories, in which all the rude and stupendous scenery of a 
granitic mountain district is displayed in its full magnificence.* 
It is therefore an unexpected and striking contrast that is pre- 
sented by a few single and regular volcanic cones perched at 
distant intervals upon the rocky ridges of these granitic em- 
branchments ; nor is it less surprising to find the gorges that 
sever them almost choked up to some distance by enormous 
flat-topped beds of columnar basalt, such as we have been ae* 
customed only to observe as the cappings of elevated hills. 

These remarkable characters belong to six different points of 
eruption, designated by the six very perfect volcanic cones of 
Moutpexat* tfunset, Thueyts, Jaujac, Souillols, and Ayzac. 

L The tirst, called by the peasant* La Orawnne de Montp&at, 
from the piusolaiui or " gravier*' of which it chiefly consists, is a 



• U *v>uM bo |suh«t* vImHouH to to p*uiU3£ than th* cold transparent 

HiuK tu tu^ wi^ ^ mouuuuti*. *c«nv« colouring of the Alp* and Pfricu oea, 

which jMv*vufc * hu^v yvjutwW vvuk their pmo»ivroa to and wateriaUa; nor 

!>m<itu*u ol boaut,* tuui um^uuyvvuw c^ ih* otuiiiio of their maaaea be con- 

th.ot *»itw <*f »lw tt%tU'>« x>t the K»* W »*Wr*U aa much inferior in grandeur. 

>fu>um *o Iitilu tmitvd by hwtitcr* of Tuo <w*uerv u» in feet thai of the Apen- 

tUo |»,ctmv*(uo. rtw \wU <"►* of ihou uii«**v but with a mom luxuriant vege- 

ctuvuiui tv»v*u, nitud S> a lot! uul fcttiou thau that groat Umaiunc range 

b* tiluuil .»lu4\«i»|'liv*v, •* Uu iuoav aduflvd oatt ^Ui^vxt. 



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Chap. Vin. RECENT VOLCANOS IN THE VLVARAIS. 187 

cone of very large size formed on a granitic ridge which sepa- 
rates the rivers Fontaulier and Aidfeche. It has a very regular 
bowl-shaped crater, gently inclined to the north ; in this direction 
the lava poured over its lowest lip into the basin of Montpezat, 
which it entirely filled to an average depth perhaps of 150 feet, 
and a width of nearly half a mile. Hence it descends the valley 
to the confluence of the Fontaulier and Burzet, where it appears 
either to have stopped, the volcano having exhausted its efforts, 
or to have mingled with a similar current which reached the 
same point from above the village of Burzet The mass of 
basalt thus deposited, as well as the subjacent granite, has been 
since cut through to depths varying from 100 to 200 feet, by 
the powerful action of the rivers whose channels it usurped ; its 
present disposition, and the beautiful columnar ranges discovered 
by this excavation, may be imperfectly judged of from the 
annexed sketch taken near the junction of the torrents Fon- 
taulier and Pourseille, about a mile below Montpezat.* Similar 
ranges extend all the way to its termination at Aulifere, where 
they are still more symmetrical, many columns being straight, 
vertical, and entire from top to bottom of the escarpment The 
engraving published by Faujas, if its faulty execution be allowed 
for, will give a tolerably correct idea of the architectural regu- 
larity of this faqade. The basalt may be observed on many 
points to rest on granite, with the intervention of a stratum of 
rolled pebbles. Its uppermost surface is bristled with rocky and 
sooriform projections, which, however, by decomposition resolve 
themselves into a rich soil affording nourishment to very pro- 
ductive chesnut forests. 

Some way above Montpezat, and perched just below the verge 
of the high primitive platform, is another cone of puzzolana and 



• See Plato XIV. 



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188 RECENT VOLCANOS IN THE VIVARAIS. Chap. Vm. 

scoriae, also seen in the engraving, which does not appear to have 
given birth to any lava-stream. 

2. Volcano of Burzet. — A bed of basalt occupies the bottom of 
the valley of Burzet, and follows all its windings as far as the point 
where it opens into the Ardeche, a distance of eight miles. It was 
produced from a point of eruption considerably above the village 
of Burzet, and at about the same elevation as the last-mentioned 
cone. It is chiefly remarkable for imbedding numerous nodular 
masses of olivine of a brilliant light green, and often as large as 
the fist It is also very regularly columnar, and I observed it has 
not unfrequently happened that the seam separating two proximate 
columns cuts through one of the large imbedded knots of olivine, 
leaving a segment on either side. This fact seems to prove that 
the columnar divisionary structure was in its origin attended by 
a powerful contractile force, and also that it did not take place till 
the lava was so far consolidated, and the knots of olivine con- 
sequently so firmly compacted in its crystalline substance, as to 
separate along the line of the* seam even when it divided them 
in two, sooner than quit their matrix.* 

In its disposition, or, more properly speaking, its aspect, this 
bed differs from the one last described ; for the river, instead of 
cutting a deep channel through the mass, and consequently ex- 
hibiting vertical sections of it on either side, generally flows 
over its surface, the upper and amorphous part of which it has 
worn away, and thus disclosed on many points a plane horizontal 
section, in which the polygonal extremities of the columns are 
united into a sort of pavement (called by the natives, as with us 
in the north of Ireland, Pavis de Giant, or Giants' Causeways), not 



* Id the face of such a fact at this, structure being occasioned by the •* mu- 
it is difficult to deny the reality of a tual pressure of spherical concretions.'* 
cmtractwn, or to speak of the columnar — See Scrope on Volcanos, p. 135 H seq. 



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CtaAF. VIH. RECENT VOLCANOS IN THE VIVARAIS. 189^ 

unlike those of the Roman roads in Italy, but arranged with far 
greater neatness and accuracy of design. 

The columns here, as throughout the Bas Vivarais, are usually 
hexahedral, often of five sides ; those of four occur rarely, of 
seven still seldomer ; I met with none of eight or nine ; and of 
three, only when interposed between larger columns in the 
manner of a pyramidal wedge. The columns are habitually of 
small diameter, not often exceeding ten or at most twelve inches. 
They are sometimes divided by very frequent joints ; at others 
attain a length of sixty feet without any separation. It struck 
me as a remarkable, and perhaps not a fortuitous coincidence, 
that, while the basaltic lava of Burzet is thickly sprinkled with 
knots of olivine, the granite, from the interior of which it has 
flowed in such abundance, contains an equal proportion of 
similarly shaped and sized nodules, composed of granular pinite 
with interspersed mica and quartz; this character prevailing 
only in a certain district near the site of the eruption. If the 
basaltic lava was derived from the fusion and recrystallization of 
granite, may we imagine the knots of pinite to have been con* 
verted during the process into olivine ? 

3. Volcano of Thueyts. — A volcanic cone to the east of the 
village of Thueyts is connected with that of Montp£zat by a 
small portion of the primary ridge on which both eruptions broke 
forth, probably at the same epoch. It is much inferior in size 
to the other, and without a regular crater ; but has vomited an 
abundant flood of lava into the bed of the Ardfeche. Thueyts 
is built upon its surface, which is cellular and scoriaceous. The 
river has gnawed out a new channel between the bounding cliffs 
of this plateau and the granite of its southern bank, and ex- 
hibited a majestic colonnade of basalt, about one hundred and 
fifty feet in height, and extending with few breaks for a mile 
and a half along the valley. 



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190 RECENT VOLCANOS IN THE V1VARAIB. Chap. VIIL 

4. The cone of Jaujac,* called La Coupe de Jaujac, from its 
cup-shaped crater, has this peculiarity, that it rises from a coal 
formation, occupying the bottom of a long transverse valley, 
between elevated ranges of granite and gneiss, and would thus 
appear to countenance the exploded notion that volcanic fires 
are alimented by* immense beds of coaL The primitive frag- 
ments, however, frequently found enveloped by its scoriae and 
basalt, sufficiently prove, if proof were wanting, that the source 
of the erupted matters existed, at least, below the sandstone 
which encloses the coal strata. 

The crater is very large and regular, but breached towards the 
north. Its figure is elliptical ; the longer axis being directed 
north and south. Its sides as well as those of the cone are 
thickly clothed with chesnut-woods ; and it is remarkable here 
as elsewhere, that those trees which grow on the volcanic are 
much larger and more productive than those on the primitive 
soil around. The earth resulting from the trituration and de* 
composition of recent basalt seems to be peculiarly favourable 
to the vegetation of the Spanish chesnut Those of the woody 
region of ^Etna are a well-known instance of prodigious luxuri- 
ance. At the foot of the cone gushes' a mineral spring strongly 
impregnated with carbonic acid gas. 

From the northern breach of the crater may be traced a vast 
current of basalt, which occupies and descends the valley of the 
Alignon to a distance of between two and three miles. The 
village of Jaujac stands upon this bed, on the brink of a mural 
precipice, which is continued to the termination of the current, 
and everywhere presents a columnar range of almost unexampled 
beauty, about 150 feet in height 

The river has excavated its channel between this and the 



* See Frontispiece.. 



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Chaf. Vm. RECENT V0LCAN08 IN THE Vr^ARAIS. 1*1 

granite of its western bank, but on the other side the bed of 
basalt, which is of considerable width, is closely soldered to the 
opposite range of primary rocks, whose debris, accumulating at 
their base into a cultivated slope, have concealed the line of 
junction. The lava of the Coupe de Jaujac either stopped 
without reaching the Ardeche, or, which is more probable, is 
confounded with that of another neighbouring cone, called — 

5. La Gravmne de SouiUols, which also disgorged its lava 
into the bed of the Alignon about 300 yards above the junction 
of this river with the Ardeche. A wide and massive plateau 
of basalt thus formed, after entering the valley of La Baume, 
prolongs itself to some distance below Niaigles, bordering the 
Ardfeche on the south with a bold and precipitous wall which 
may be seen to rest on a layer of pebbles, the ancient bed of 
the river. 

The face of this line of cliff, as well as that of the current of 
Jaujac, exhibits two distinct portions or stories separated by a 
well-defined straight line generally parallel to both surfaces ; the 
upper consists of small, irregular, and matted columns; the 
lower, habitually occupying about one-third of the whole height, 
of large, perfect, and vertical pillars, which almost appear placed 
as an artificial support to the immense superincumbent entabla- 
ture. On a close inspection the regular columns below are seen 
to proceed so immediately out of the upper and comparatively 
amorphous mass, that it is evident the whole was cast at once, 
and the two portions cannot be considered as different beds or 
currents.* Their singular difference of structure may be ac- 
counted for, I conceive, by supposing the upper part to have 
been first consolidated by exposure to the air, while the lower 
was still in motion, and flowing down the river channel beneath. 



* See Frontispiece 



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in BECEST VOLCAS06 IS THE TIYABAI& (Sue. Vffl. 

When the efflux of lava from the Tent finally ceased, this latter 
maw will hare cooled down with extreme skrwnesB, and bee* 
consolidated in a regular and tranquil manner, each as would 
facilitate the establishment of straight and vertical axes of eon* 
traction, and the production of very regular hexahedral columnar 
concretions, perpendicular, as usual, to the cooling surfaces.* 
A view of part of this range near the Pont de Banme en* 
graved in the work of Faujas, after due deductions for exaggera- 
tion in size and its faulty execution, gives not an inaccurate 
idea of the disposition of the columns. 

It is liere that the river, descending both from Burnet and 
M<mt[>6mt f joins the Ardeche ; so that, if we suppose their erup- 
tions to liavo been contemporaneous, or nearly so, it is not at all 
improbable tliat the five lava-currents we have described, flowing 
from as many different points, were once united on this spot, 
exactly as the rivers were, and still are, whose channels they 
umirjHul, In the bed of the river *Ardfeche, at and for some 
distance below tliw point, may be seen in summer, when the 
stream is inconsiderable, a number of articulations of basaltic 
(minimis, in which a nice observer may recognise the mineral 
diameter* of the different lava-currents of the tributary valleys. 
As yon follow the course of the river, these columns show them- 
solves less frequently and are more water-worn, till at the 
distance of a milo or two they are reduced to little more than 
rounded blocks, and nearly assimilated to the other boulders 
which cover the dry channel of the river. These basaltic 
boulder* continue to diminish in sixe as you descend, and few 
mo to ho met with as far down the stream as Aubenas so large 
it* it man's head ; fttrther on they are reduced to mere pebbles, 
and ww no doubt still more ixtmminuted before the Ardfeche 



• Ho* iVu»uWi*tioM on Yok*iio*i p. 136. 



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Chap. VIE. RE-EXCAVATION OF RIVER CHANNELS. 193 

carries them with it into the Rhone. This observation illus- 
trates the process by which both the basalt and granite that once 
filled these valleys have disappeared. A wintry flood under- 
mines and detaches a prism of basalt from one of the columnar 
ranges. The next flood drives it on a few inches ; or, if by its 
form and position it is enabled to roll without much difficulty 
onwards, a few feet This operation is repeated year after year, 
and in the mean time, even when remaining stationary, it is 
exposed to the immense friction of all the smaller boulders and 
pebbles which are drifted over it by the ordinary as well as the 
extraordinary force of the current By the continuance of this 
process it is at the same time carried forwards, reduced in size, 
and brought to approach to a globular form, the most favourable 
to its transport, in consequence of which the rapidity of its 
progress along the channel of the river is progressively accele- 
rated, till, diminished to the size of gravel or silt, it is taken into 
complete suspension, and carried sooner or later in this state into 
the ocean. 

At the foot of the cone of Souillols, near the hamlet of 
Neyrac, rises a spring strongly impregnated, like that of Jaujac, 
with carbonic acid gas ; and from the bottom of a small hollow 
close by this gas emanates in such abundance that the exact 
phenomena of the Grotta del Cane are reproduced, and dogs or 
fowls may be stifled and revived ad libitum. 

6. The last of the cones we have mentioned, called La Coupe 
d Ayzac, rises on the ridge of one of the granitic abutments that 
project from the steep escarpment of the Haut Vivarais. It has 
a beautiful crater slightly broken down towards the north-west ; 
and from the breach a stream of basalt may be seen to descend 
the flank of the hill, and turning to the north-east enter the 
valley of the river Volant, which has subsequently cut it 
entirely across, and disclosed three distinct storied ranges ; the 



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55 



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^p. VIII. BASALTIC DYKE NEAR AUBENAS. 195 

*h respect to ourselves. I am not aware of any organic re- 
iins having been observed under these lava-bfeds, which might 
row any light on the geological age to which they belong. 
There is one instance, in the immediate vicinity of Aubenas, 
which a volcanic eruption appears to have taken place 
ithin, but at little distance from, the limits of the secondary 
mestone formation. The hill upon which this town, is built 
onsists of strata dipping to the south at an angle of 10°. 
.Vithin a hundred yards north of the town walls, and scarcely 
*> much from the sandstone on which they rest, these limestone 
strata are abruptly broken through by an enormous vertical 
dyke of basalt, which protrudes about 30 feet above the summit 
of the hill, and may be traced down its side into the valley of 
the Ardiche, pursuing an easterly direction. At the lower part 
of the hill the dyke measures from 12 to 20 feet between its 
cheeks ; higher up it increases in bulk, and at the summit is 
90 feet thick. From thence it makes a sudden curve to the 
north, returns to the north-east, and is again to be traced down 
the same face of the hill about a hundred yards from the other 
branch ; thus including a large portion of the limestone strata, 
which preserve their parallelism and general inclination. This 
second branch of the dyke has dislocated and shattered the 
limestone within a space of from 40 to 50 yards, enveloping 
blocks and fragments of all sizes, with which it is mixed con- 
fusedly, and presents the appearance of a loose limestone breccia 
traversed or cemented by veins of basalt Two smaller veins 
may also be observed cutting perpendicularly the undisturbed 
limestone strata enclosed by the two arms of the principal dyke. 
The one is 15, the other 10 inches thick. 

The basalt itself is of a very dark grey colour, compact, 
fine-grained, hard, and tough ; its fracture tends imperfectly to 
the conchoidal, and it breaks into curved and angular pieces. 

o 2 



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Chap. VIII. BASALTIC DYKE NEAR AUBENAS. 195 

with respect to ourselves. I am not aware of any organic re- 
mains having been observed under these lava-beds, which might 
throw any light on the geological age to which they belong. 

There is one instance, in the immediate vicinity of Aubenas, 
in which a volcanic eruption appears to have taken place 
within, but at little distance from, the limits of the secondary 
limestone formation. The hill upon which this town is built 
consists of strata dipping to the south at an angle of 10°. 
Within a hundred yards north of the town walls, and scarcely 
so much from the sandstone on which they rest, these limestone 
strata are abruptly broken through by an enormous vertical 
dyke of basalt, which protrudes about 30 feet above the summit 
of the hill, and may be traced down its side into the valley of 
the Ardiche, pursuing an easterly direction. At the lower part 
of the hill the dyke measures from 12 to 20 feet between its 
cheeks ; higher up it increases in bulk, and at the summit is 
90 feet thick. From thence it makes a sudden curve to the 
north, returns to the north-east, and is again to be traced down 
the same face of the hill about a hundred yards from the other 
branch ; thus including a large portion of the limestone strata, 
which preserve their parallelism and general inclination. This 
second branch of the dyke has dislocated and shattered the 
limestone within a space of from 40 to 50 yards, enveloping 
blocks and fragments of all sizes, with which it is mixed con- 
fusedly, and presents the appearance of a loose limestone breccia 
traversed or cemented by veins of basalt Two smaller veins 
may also be observed cutting perpendicularly the undisturbed 
limestone strata enclosed by the two arms of the principal dyke. 
The one is 15, the other 10 inches thick. 

The basalt itself is of a very dark grey colour, compact, 
fine-grained, hard, and tough ; its fracture tends imperfectly to 
the eonehoidal, and it breaks into curved and angular pieces. 

o 2 



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ttituc rii^fli** *-vuit «ii**i 

1/ inu*r v- terr**ft i ■*_»iii*r -eannDi£» rf 

*;»!* r'mft* r>jti* tmc jf .mtu-wra. «j» absent 

i'/'4^ ?.iu* 'u^nmnfluij'^ wiriLrr ^n^eufr ni 

+af K s&afr: *y inw- v. jr-jy&ti iron, "ait o**ns» if nsbo- 1 

4ft*3*W -: wit ,ti j» *a*r*d.r* v. tut auafeimt fncm:* a? ^fc. JLJyst. 

*<. ,*S ***iUu?» . Htmrxa*. OiaJnwiL kbc "a* mmi mi nam *f * 

*muu»r jutftur«r «a*a. ** *aa» iiar:L*T anas *; i*""t 

iriOtr Wn-rj. u^t w*- *& *j:ok- i:»:k i:r jot «C3L. A ins** 
y^jrV* '/ v>t 13^. mjttfti *rim wmk elf ibcae sens *» 

tte 'Ana* **yi **i*r ftKoasie j**n» g rpwj g irca* 
M »>;y& ur:;sj*r*r& iz£.pPb*aoa§ ar* fdH < ^ 

l/t <;*? for**,?*] i**iandat*4i of ti^eir «faeJk cave iw to 
**/*,r *r*t* '/ tl***e laltt^baans ; wtCe c«i thaw ff«tf» 
to: *j/r;/^ yr*Aw*A the matter in attendance, or in the 
«r# '**!* "f *****< or b?<* compact fend-crystalline hnratiae, 
•0 travertin, m<TH f<*u*d by hs precipitation. This ww » 
*f**$'jSy <*nttirm**\ by the a dmixtur e with the lime both of 
«fJi/**Mft matt/T, whi/-h is known to be frequently deposited 
fr'*n thermal *pring» in a volcanic country, and aho of gyp- 
mttn ; for it ha* been shown thai eruptions were habitually 
taking jda/** during the deposition of the calcareous strata of 
tlw Lirriagne and the Cantal, if not of the Haute Loire: 
nwl if *tilphuretted hydrogen was evolved, as is usual during 
th<**« phenomena, through the soft marly beds at the bottom 
of tlw \nUcn, the Hiilphuric arid uniting with the lime would 
h*n nmri\y pniduee flint mineral : of which a part may have 




i 



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Chap. EL CONCLUDING REMARKS. 199 

been precipitated on the spot, and the remainder carried away 
by the water into the lower lake-basins to be ultimately de- 
posited there (Gypsum of Paris ?). The strong odour of sul- 
phuretted hydrogen emitted from the marly limestone of Le 
Puy seems indeed to prove that this gas was produced at the 
epoch of its deposition. 

In fact, the calcareous freshwater formations of the centre of 
France differ but in this one respect (viz. the presence of 
gypsum and silex, which the thermal volcanic springs will 
account for) from the recent shell-marl deposits of the Bakie 
and other lochs in Scotland, described by Sir C. LyelL In 
both are found Limne®, Planorbes, Helices, a species of Cypris, 
the remains of Charae and the Gyrogonites. In both, marly 
strata in which all traces of shells have disappeared, but which 
occasionally contain bones of mammalia and birds, alternate 
with others of a yellowish travertin limestone, often semi-crys- 
talline, tubular, containing remains of vegetables, insects, &c., 
and with beds of sand. The basins of both still contain springs 
charged with carbonate of lime, and both occur in the neigh- 
bourhood of trap or volcanic rocks.* 

4. With regard to the rocks of volcanic origin, they are 
distinguished primarily into, 1st The products of three great 
habitual vents — the Monte Dore, Cantal, and Mezen, which 
appear to have been in activity towards the same time, and to 
have raged at intervals and with intense energy during a 
period of considerable duration. 2ndly. The products of single 
occasional eruptions from a vast number of separate apertures, 



* I retain these remarks as they ment and confirmation they have since 

were printed in the first edition (1826), received in the works of my friend 

although aware that to the greater num- Sir Charles Lyell. See his Manual, 

ber of my readers such arguments will p. 197-203, ed. 1855. 
be familiar from the admirable develop- 



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X* ' yrLTDCfrr IHMaJJL*. Ca*f>»I2L 



roamed *Io»ty aioae die line -if what w fanfaahiy a \ 
prwnvi ft a rtaw * in 3n* «p«d*Ta! amain*, g i pgjnn c 6n& i 
nnrth~w*!*r **> wsdkHnmk^aifCL Mnxwthe wfuiie *±ie*aaed tract. co» 
hv*i*i**nt Tr.rk 4u* jpnesu ozih"Caiil • <t n» jeda* and rf—ip6«» vita 
the *ri» '-vf mevadiiiL. £•'& ^iaaaaa if voicanie p t mbgte -»«fc3*i* 
* 2w*t variety of Tifm*^! 'wapwomL Anaa pwrow ftA fe p at h o aa 
fcwhyv to Twpatt awe r> haaair B»*h rest iiaiMei c t ftr 
upon A* atanin* mdo and she freshwater jtrala* ami erea ia 
*vm^ hwtaaiwi art found V alienate with die kttez; as far 
*xamp>K du«r trartyfe at the Caafel aear laallac ami the 
fcawwt <vf G^Tjwia. the Pot Dallec Pant da Chafieaai Sac The 
latter raranHFtaaee lafidndr pruvw efwftuoa to have takem 
pk**s JwlfMaDj frm bah the fne^al Toieanw aai the 
kyaprtoriinal fiwnre , darine the period of the d epositio n of the 
fwhwater fcraatioa. Bat it is equally certain that a large 
prttfffrtitm (4 the basaltic lavas were erapted safaseqaeiitty to 
the emptying of die freshwater lakes of the Liaagne aad the 
Hsttte Loire, since they hare filled hollows and valleys eaten 
tmi <A tbdr atnrtifled deposit*. 

An attempt haa been made by many of the French geologista 
Up mm\*} the production of the volcanic rocks of Central France 
Up two or three distinct periods alone, upon grounds either of 
fff/tiliar mineralogical character, or their superposition to parti- 
ralar alluvial beds. It appears to me, however, that no classifi- 
vntum in respect to age, founded on such data, can be relied 
upon. The most popular division perhaps is that of H. Rozet,* 
who rvfvm them to three distinct epochs, which he calls " The 
Trwbytic, Itasaltir, and La vie," But it is unquestionable, from 
tin* ffiont direct evidence of superposition, that many of the 
I mm It* worn produced as early as a large proportion of the tra- 

* Bulletin XIV. p. Uil. 



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Chap. EX. AGE OF THE VOLCANIC ROCKS. 201 

chytes ; and, on the other band, many trachytes, for example 
Hie domitic puys, are so associated with the most recent cones of 
scoriae and lava currents, that they must be considered of the same 
age : to which it may be added that the best defined trachytes are 
occasionally found to pass into clinkstone, and this again into 
basalt* Some of the freshest lavas of the Monts Ddme, as those 
of Nugere and Volvic, are indeed almost wholly composed of 
felspar, and differ little if at all from many of the trachyte 
currents of the Mont Dore.f All, in truth, that can be said 
on this point is that, generally speaking, the eruption of trachyte 
preceded that of basalt, but that there were on several points 
alternate emissions of the two sorts of lava is not open to 
question; and this accords with what has been observed in 
other volcanic regions, where the general rule seems to have 
been the earlier production of trachyte, although exceptions are 
frequent^ 

As to the alleged uniform superposition of the basaltic cur- 
rents to alluvia, containing rolled pebbles of basalt, as mnrlring a 
particular age (which is the idea of M. Pissis §), it is quite certain 
that this feature is common to basalt of every age from nearly 
the first to the last produced ; and necessarily so, since the lava 
stream will always have flowed into the channel of the then 
existing rivers, which must generally have contained alluvial 
gravel and rounded pebbles, the debris of the neighbouring 
slopes ; in fact, such beds are found beneath what are evidently, 
from their circumstances of position, aspect, decomposition, and 
denudation, the oldest as well as the newest lava-currents. For 
these reasons I can admit no other criterion of the relative age 



♦ See M. Raulin's paper on the Can- chytic domes and currents have bunt 

tal. Bulletin XIV. p. 1 14. through the earlier basaltic beds, 
t See note to p. 131, supra. § Bulletin XIV. p. 244), &c. 1843. 

£ In Iceland as weU as Tenerifle tra- 



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202 CONCLUDING REMARKS. Chap. IX* 

of the volcanic products I hare described, than such as is de- 
rived from the circumstances above mentioned ; especially, and 
before all, their position in relation to the levels, and the amount 
of degradation they, or the surrounding rocks, have evidently 
undergone since they were poured out as more or less liquid 
lavas upon the spots they now occupy. Upon this point some 
further remarks are necessary. 

5. It is impossible to observe the many strips of the originally 
continuous freshwater formation which rise from the plain of 
the Limagne in long tabular hills, transverse to the general 
course of the river which now drains the principal valley-plain, 
without being convinced that each owes its preservation from 
the destruction which has swept away the remainder of the 
formation to its capping of basalt, which, by reason of its 
superior hardness, would naturally protect the underlying 
strata from the rains, frosts, and other meteoric agents, to 
which the uncovered intervals of the marly plain left by 
the emptying of the lake were permanently exposed. Such 
a capping, on the other hand, would afford a very inefficient 
protection against the denuding force of any violent deluge or 
general current of waters, to which some writers have attributed 
the excavation of the valleys intervening between these high 
basaltic platforms : more particularly as the direction of any 
such current passing over this district must have been coincident 
with the general direction of the valley of the Limagne, or from 
south to north ; whereas the long strips and flat promontories in 
question invariably run east and west, preserving, as might be 
expected, the direction which was originally given by the lateral 
slopes of the valley-basin to the streams of lava that flowed into 
it from the heights on either side. 

Again, had the whole excavation effected in the freshwater 
formation of the Limagne been produced at once, by any debacle 



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Chap. IX. EXCAVATION OF THE L1MAGNE VALLEY. 203 

accompanying an elevatory movement of the granitic base, or 
the eruption of some of the volcanos, or by any diluvial or other 
violent catastrophe, it is clear that the remnants of the lava-cur- 
rente which had flowed into the freshwater basin before this epoch 
would be necessarily all found at one level, or nearly so, corre- 
sponding to the average level of the bottom of the lake-basin at 
that time ; while, on the other hand, all the lava-streams which 
have flowed since the debacle or supposed deluge would be found 
at another nearly uniform, but much lower level, viz. that of the 
lowest places of the excavated valley. But, as we have seen, no 
marked distinction of this sort exists ; no line can be drawn to 
separate the basaltic beds met with at high or low levels. They 
are found at all heights, from 1500 feet downwards, above the 
water-channels of the proximate valleys ; and some even of the 
most distant in point of level are situated geographically close 
to one another. . 

Let Us take, for instance, the two neighbouring basaltic plat- 
forms of Gergovia and La Serre, and the bed of basalt which 
occupies the bottom of the narrow valley that divides them, and 
which has flowed out of the recent vent marked by the Puy 
Noir.* Here are three long strips of basalt, each of which, by its 
gradual inclination in the direction of its greatest length, and by 
the positive remains of the cone of scoriae in two instances at least 
out of the three, are proved to have flowed in a state of liquidity 
from volcanic vents opened upon the high granite platform, into 
the basin of the freshwater formation. Each must necessarily 
have occupied the lowest levels of that basin to which it had 
access ; and therefore it is evident that, at the period when the 
lava of Gergovia flowed into its present position, there could 
have been no lower depression in the immediate vicinity. The 



* See p. 91, and also Plate I., and the Map of the Monte Dome. 



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Chap. VIII. BASALTIC DYKE NEAR AUBENAS. 195 

with respect to ourselves. I am not aware of any organic re- 
mains having been observed under these lava-beds, which might 
throw any light on the geological age to which they belong. 

There is one instance, in the immediate vicinity of Aubenas, 
in which a volcanic eruption appears to have taken place 
within, but at little distance from, the limits of the secondary 
limestone formation. The hill upon which this town, is built 
consists of strata dipping to the south at an angle of 10°. 
Within a hundred yards north of the town walls, and scarcely 
so much from the sandstone on which they rest, these limestone 
strata are abruptly broken through by an enormous vertical 
dyke of basalt, which protrudes about 30 feet above the summit 
of the hill, and may be traced down its side into the valley of 
the Ardiche, pursuing an easterly direction. At the lower part 
of the hill the dyke measures from 12 to 20 feet between its 
cheeks ; higher up it increases in bulk, and at the summit is 
90 feet thick. From thence it makes a sudden curve to the 
north, returns to the north-east, and is again to be traced down 
the same face of the hill about a hundred yards from the other 
branch ; thus including a large portion of the limestone strata, 
which preserve their parallelism and general inclination* This 
second branch of the dyke has dislocated and shattered the 
limestone within a space of from 40 to 50 yards, enveloping 
blocks and fragments of all sizes, with which it is mixed con- 
fusedly, and presents the appearance of a loose limestone breccia 
traversed or cemented by veins of basalt Two smaller veins 
may also be observed cutting perpendicularly the undisturbed 
limestone strata enclosed by the two arms of the principal dyke. 
The one is 15, the other 10 inches thick. 

The basalt itself is of a very dark grey colour, compact, 
fine-grained, hard, and tough ; its fracture tends imperfectly to 
the eonchoidal, and it breaks into curved and angular pieces. 

o 2 



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Chap. IX. AGE OF BASALTIC PLATEAUX. 206 

Examples of this kind might be multiplied endlessly were it \ 

necessary, leading inevitably to the conclusion that the im- 
mense abstraction of matter which has occurred in the fresh- 
water formation of the Limagne was for the most part effected 
gradually and progressively, and went hand in hand with the 
occasional flooding of parts of this valley and its tributary 
ravines by lavas emitted in the eruptive paroxysms of the vol- 
canos on the neighbouring heights. Even were it allowable to 
have recourse to vague and hypothetical conjectures, we can 
conceive no gradual and progressive excavating forces, other than 
those which are still in operation wherever rains, frosts, floods, 
and atmospheric decomposition act upon the surface of the 
earth. To these agents, then, we must refer the effects in 
question, of which, with an unlimited allowance of time, no one 
will pronounce them to be incapable. 

The composite sections of a part of the Limagne, seen in Plate 
XVII., in which the most remarkable currents of basalt that 
have descended at different epochs into this basin are given at 
their respective heights, will show how completely these volcanic 
remains mark in their actual position the progressive steps of 
this excavation, and exhibit a natural scale for measuring the 
duration of the process; a scale to complete which little is 
wanting but a knowledge of the intervals which elapsed between 
the successive eruptions by which these lava-currents were 
poured forth from the ridge of the Monte D6me. 

The lavas of the Bas Vivarais offer equally incontestable proofs 
of the same fact We see there a number of deep and narrow 
valleys worn in the flanks of a steep range of granite, which 
have, at a certain epoch, been occupied, through a length of 
several miles, by lava poured in a liquid state from neighbouring 
volcanic vents, which has evidently filled them up to a high 
level, exactly as melted metal fills a mould into which it is 



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206 CONCLUDING REMARKS. Chap. IX. 

j>oured. Since that epoch the valleys hare been re-excavated 
in many parts to more than their former depth and width, the 
now cliannel being cut in some cases through the basaltic lava, 
in others through the granitic sides of the original valley. Now, 
if the first excavation of these valleys is to be accounted for by 
the hypothesis of a deluge, to what are we to attribute the 
MHxmd process ? Not, most certainly, to a second deluge ; for 
tht> undisturbed condition of the volcanic cones, consisting of 
Iihw scoria? and ashes, which actually let the foot sink ankle- 
deep in them, forbids the possibility of supposing any great 
wave or debacle to have swept over the country since the pro- 
duction of these cones. The amount of excavation which has 
taken place subsequently to the epoch of these eruptions can 
then haw been only effected by the streams which still flow 
there ; ami as this quantity bears a very considerable proportion 
to the extent of the original excavation, there can be no reason- 
able grounds for hesitating to attribute the latter to the same 
agency which effected the former ; it being only necessary to 
a**igu a lunger duration to the process to account for the differ- 
ence iu magnitude of the result Those who, having before their 
eye* the proof that the immense quantity of solid rock removed 
(Wm Uww valleys since their occupation by the lava has been 
etVtvUnl by natural causes, such as are still in operation, will 
yet iwur to a vague and unexampled hypothesis for the purpose 
of explaining the removal of a simitar, or not very much greater, 
quantity* prior to that epoch, must do so in defiance of all the 
Uv\* of analogical reasoning, by strict adherence to which we 
mil alone W|>e to obtain the least acquaintance with those 
tolerations ttf Nature's laboratory of which we have not been 
actual e\ o~* itiuvtsca. 

The volcanic district of the Haute Loire presents another 
chain of proofs equally conclusite of the same fact It is im- 



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Chap. IX. GRADUAL EXCAVATION OF VALLEYS. 



207 



possible to doubt that the present valleys of the Loire, and all 
its tributary streams within the basin of Le Pny,* have been 
hollowed out since the flowing of the lava-currents, whose corre- 
sponding sections now fringe the opposite margins of these 
channels with columnar ranges of basalt, and which constitute 
the intervening plains. Yet these lavas are undeniably of con- 
temporary origin with the cones of loose scoriaB which rise here 
and there from their surface, and which would necessarily have 
been hurried away by any general and violent rush of waters 
over this tract of country. It is indeed obviously impossible 
that any such flood should have occurred ; and we are therefore 
driven to conclude that the erosive force of the streams which still 
flow in these channels, together with the action of direct rains, 
frost, and other meteoric phenomena, have alone hollowed out 
this extensive system of deep, and, in some instances (as that of 
the Loire itself), wide valleys.! 



* See Plate XL 

t [It is scarcely necessary to attempt 
a serious refutation of a species of 
quibble which has been too often 
brought forward in place of argument 
by the diluvian theorists; viz. that 
rivers are caused by the pre-existence of 
the basins through which they flow, and 
consequently these could not have owed 
their existence to the rivers that flow 
through them ! It is clear that no ex- 
tensive surface of the earth could at any 
time have been so uniformly smooth and 
level but that the rains falling upon it 
must have coUected into streams as they 
drained off. The erosive force of these 
streams would necessarily by degrees ex- 
cavate channels of a width and depth pro- 
portioned to the duration of the process, 
their magnitude and velocity, and the 
more or less destructible nature of the 
rocks over which they flow. 



Of course, it cannot be doubted that 
vast irregularities of level, elevations 
and depressions of the earth's surface, on 
every scale of magnitude, have been 
occasioned by other causes, chiefly sub- 
terranean expansion. Mountains and 
valleys, in other words, the basins of 
our seas, lakes, and rivers, no doubt owe 
to circumstances of this nature their 
primary forms. Submarine currents, and 
the wearing action of the waves against 
litoral cliffs, will have scooped out many 
hollows in rocks exposed to these ero- 
sive forces; and convulsive oscillations 
of the ocean, or other aqueous re- 
servoirs, occasioned by the sudden 
heaving up of large masses of the 
earth's crust, may have subsequently 
sent repeated waves over parts of our 
continents, the effect of which would 
be to open communications between 
distant basins, to create new and ex- 



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206 



CONCLUDING REMARKS. 



Chap. IX. 



The time that must be allowed for the production of effects of 
this magnitude by causes evidently so slow in their operation is 
indeed immense ; but surely it would be absurd to urge this as 
an argument against the adoption of an explanation so unavoid- 
ably forced upon us. The periods which to our narrow appre- 
hension, and compared with our ephemeral existence, appear of 
incalculable duration, are in all probability but trifles in the 
calendar of Nature. It is Geology that, above all other sciences, 
makes us acquaiitfed with this important though humiliating 
feci Every step we take in its pursuit forces us to make almost 
unlimited drafts upon antiquity. The leading idea which is 
present in all our researches, and which accompanies every fresh 



tensive denudations, and accumulate 
vast beds of transported fragments along 
the course of these mighty currents. 
But the proofs of the passage of such 
destructive deluges oyer any country 
require to be strictly made out and care- 
fully tested. It wUl be seldom possible 
to show that the results cannot have 
been occasioned by the bursting of lake- 
basins, or other minor agencies still in 
operation, acting during an unlimited 
period. Before any just estimate can 
be formed of what share must be attri- 
buted to extraordinary catastrophes, 
and what to these minor but constant 
excavating forces, of the whole amount 
of change which has been evidently pro- 
duced by the action of water in motion 
on the surface of the land, it is absolutely 
necessary to acquire a much more de- 
finite knowledge of the laws which re- 
gulate the circulation of water over the 
earth's surface, and its effect upon that 
surface, than we can at present he ad- 
mitted to possess. It is too true that the 
greater number of geologists have sat 
down without hesitation to investigate 
by a sort of guesswork the origin of the 



changes and mode of production of the 
mineral masses which they observe on 
the surface of the globe, in complete 
ignorance, or at least with a total neglect, 
of those processes which are still daily 
employed by nature in the creation of 
fresh changes, and the production of 
new mineral masses on the same surface, 
bearing a complete analogy, to say the 
least of it, to the earlier phenomena, 
and older formations, which it is the 
business of geology to account for.] 

This passage has been retained in the 
present edition, although the argument 
may appear unnecessary in the present 
advanced state of geological science, and 
especially after the publication of Sir C. 
Lyell's admirable * Principles ; v for the 
reason that neither my eminent friend, 
nor the bulk of geologists are, I think, 
even yet sufficiently impressed with the 
immense amount of excavation or denu- 
dation effected on supra-marine land by 
the erosive force of the pluvial and 
fluvial waters — in other words, by ' Rain 
and Rivers.' That story is yet to be 
written, but not by the eccentric author 
of the recent work under that title. 



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Chap. IX. GRADUAL EXCAVATION OF VALLEYS. 209 

observation, the sound which to the ear of the student of Nature 
seems continually echoed from every part of her works, is — 

Time !— Time !— Time ! * 

At least, since by a fortunate concurrence of igneous and 
aqueous phenomena we are enabled to prove the valleys which 
intersect the mountainous district of Central France to have 
been for the most part gradually excavated by the action of 
such natural causes as are still at work, it is surely incumbent 
on us to pause before we attribute similar excavations in other 
lofty tracts of country, in which, from the absence of recent 
volcanos, evidence of this nature is wanting, to the occurrence 
of unexampled and unattested catastrophes, of a purely hypo- 
thetical nature. 

Nevertheless, although the evidence of their more or less de- 
graded appearance and position proves the volcanic rocks of 
Central France to have been erupted at many different periods, 
and not at any one, two,' or three epochs alone, yet there is 
reason to suppose some of these eruptive periods, more or less 
prolonged, to have been of extreme or paroxysmal energy. This, 
indeed, would only be in accordance with the habitual laws of 
volcanic action. To the earliest of such periods we may ascribe 
the production of the three chief volcanic mountains — the Mont 
Dore, Cantal, and Mezen. This outburst seems to have com- 
menced towards the close of the deposition of the Miocene lacus- 
trine strata. Several, likewise, of the independent basaltic beds 



* It it very remarkable that, while minds that would not for an instant 

the words Eternal, Eternity, For ever, are doubt the God of Nature to have existed 

constantly in our mouths, and applied from aU Eternity, and would yet reject 

without hesitation, we yet experience as preposterous the idea of going back 

considerable difficulty in contemplating a million of years in the History of 

any definite term which bears a very His Works. Tet what is a million, or a 

large proportion to the brief cycles of million million, of solar revolutions to 

our petty chronicles. There are many an Eternity f 



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210 CONCLUDING REMARKS. Chap. IX. 

that cap the highest hills of that formation, as well as those of 
calcareous peperino in the middle of the basin, belong evidently to 
a date quite as early. The larger proportion of the chain of puys of 
the Monte Dome and the Haute Loire, especially the latter, must 
be attributed to another and comparatively recent eruptive era, 
which, from the evidence of organic remains found in the under- 
lying alluvia, is referable to the Pliocene age. In the long interval 
between these two periods very many eruptions certainly took 
place from openings on the flanks of the volcanic mountains, as 
well as along the eastern zone of the Limagne and Forez — erup- 
tions whose lavas are found at varying heights above the existing 
river courses, and which therefore cannot be referred to any 
single epoch. And again, the most recent lavas and cones of 
the Mont Dome and the Bas Vivarais have evidently broken forth 
at a yet later period, the Post-pliocene; probably even since 
the appearance of man in the country, although several species 
of the larger mammifers, now extinct, were contemporaneously 
its inhabitants. 4 ' 

6. Another question of considerable interest presents itself 
namely, what were the original limits of the several lake-basins 
of Central France, and the levels at which their waters stood ? 

In regard to those of the Upper Loire (of Montbrison and 
Le Puy) little difficulty exists, since the granitic barriers remain, 



* A remarkable analogy exist* on all in relation to the adjoining valleys, ex- 

these points between the several volca- cavated, as in Auvergne, through ter- 

nic rocks of Central France and those of tiary freshwater limestone ; the earliest 

the district in Asia Minor, called by forming plateaux elevated 600 feet or 

Strabo the ' Katakekaumene,' as was in- more above the present river-beds, the 

deed noticed by Messrs. Hamilton and latest occupying the channels of these 

Strickland in their description of the streams (which, however, they have 

latter. (Geol. Trans., vol. vi. 1816.) often cut through), while others oc« 

Tbey likewise are shown to have been cupy intermediate positions between 

erupted at several distinct periods by these two extremes, 
the position occupied by the lava beds 



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Chap. IX. LEVEL OP LAKE-BASINS. 211 

within which, if the narrow defiles that form the outlets of these 
basins were filled up, the superficial waters even now would rise 
to the highest levels at which any sedimentary strata are found. 
Such, however, is not the case of the Limagne and Cantal lake- 
basins. The tertiary beds of the first can be continuously traced 
from Brioude in the south to Decize near the confluence of the 
Loire and AUier in the north ; and the lake would seem there- 
fore to have been equally continuous. But in the vicinity of the 
latter spot we find no granitic or secondary heights capable of 
confining a body of water at a level of 2700 feet above the sea, 
which is the elevation attained by some of the lacustrine strata 
near Clermont and Issoire.* The highest hills now existing 
near the northern termination of this lacustrine formation do not 
attain 1000 feeif It seems difficult to suppose a thickness of 
1700 feet of rock to have been removed from the low hills north 
of Moulins, since the tertiary era ; and it is more reasonable 
to imagine that changes of relative level have taken place, by 
which the southern portions of the tertiary formation may have 
been elevated, or the northern depressed. 

M. Eaulin, indeed, thinks he can trace the existence of a 
transversal east and west axis of elevation across the line of the 
Limagne, in the parallel of the Mont Dore and the Puy Barnere, 
the highest jfoint at which the tertiary strata are left.} M. Pissis § 
is of opinion that the whole freshwater formation has been ele- 
vated since its deposition, so as to give it a slight general dip 
from west to east, and from south to north. 

It appears unnecessary to decide exclusively for any one of 
these hypotheses, which may be all more or less accordant with 
fact Although the absence of secondary strata through the 

* At the Puy Girou, 2700 feet ; at vera and Magny (Oxford clay), 960 feet. 
the Puy Barnere, 2730. J Bulletin XIV. p. 587. 

f Height of signal-post between Ne- § Bulletin, 2de Ser. p. 46, 1843. 

p2 



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212 CONCLUDING REMARKS. Chap. EX. 

entire granitic region proves it to have formed an island in the 
ancient ocean where those strata were deposited, it is quite pos- 
sible that it may have sustained considerable absolute elevation 
since the formation of its tertiary beds, and especially during its 
eruptional era ; indeed it would be unlikely that Central Franc* 
should have remained unmoved during the elevation of portions 
of the neighbouring Alps and the basin of Switzerland from 
beneath the sea to a height of 5000 or 6000 feet And again, 
with our knowledge of the repeated alternations of marine and 
freshwater deposits in the basin of Paris, into which the cal- 
cariferous waters of the Limagne overflowed, it is impossible to 
question the probability of occasional subsidence along the line 
of the intervening heights. 

I am however of opinion that whatever changes of relative 
level took place, they operated over wide superficial areas, since 
few or no traces of disturbance are visible in the sedimentary 
beds of the Limagne. The surfaces over which the basaltic cur- 
rents flowed, and which, having been since protected by them 
from the rain-fall, preserve the highest remaining surfaces of the 
lacustrine formation (although at that time they must have been 
its lowest levels), exhibit just that gradual inclination away from 
the bordering heights, where the greater number were erupted, 
which might be expected to prevail in the bottom of a shallow 
but gradually deepening lake. No sudden faults or dislocations 
appear to indicate any relative changes of level within areas 
of moderate extent.* On the other hand, the vast amount of 



• This remark, however, must be 600 and 700 feet above the correspond- 

confined to the Limagne. The fresh. ing strata in the contiguous valley of 

water strata of the Cantal have evi- the Cer; and some portions of these 

dently suffered a certain amount of tertiary beds (vis. at Dienne) have been 

disturbance. M. Raulin describes the lifted up to an absolute elevation of 

calcareous beds in the vaUey of the 3680 feet — a position in which it is dif- 

Alagnon as reaching a height of between ficult to suppose they were deposited. 



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Chap. IX. CHARACTERISTIC FEATURES. 213 

denudation to which the freshwater formation of the Limagne 
has been subjected, and which has left (as M. Bamond expressed 
it) only a few detached hill s as relics of a former plain elevated 
many hundred feet above that now existing, may well be believed 
£o have been accompanied by a corresponding destruction of 
superficial rocks at the northern end of the plain. I have at- 
tempted to show, not unsuccessfully, I hope, that a large proportion, 
if not the whole, of the degradation sustained since the tertiary 
period, as well by the granitic platform itself and its surrounding 
secondary zone, as by the freshwater strata, was effected by the 
slow and gradual but long-continued erosive force of the ordinary 
meteoric agents of denudation, rain, torrents, and river-floods, 
co-operating, as in this district they most probably did, at least 
during its eruptive periods, with frequent earthquake shocks, and 
perhaps a general elevation of the southern portion of the platform. 
I cannot conclude the detailed description I have attempted 
to give of this interesting country, better than by quoting the 
eloquent summary of its characteristic features which Sir 
Charles Lyell has given.* 

44 We are here presented with the evidence of a series of events 
of astonishing magnitude and grandeur, by which the original form 
and features of the country have been greatly changed, yet never so 
far obliterated bat that they may still, in part at least, be restored 
in imagination. Great lakes have disappeared — lofty mountains 
have been formed, by the reiterated emission of lava, preceded and 
followed by showers of sand and scoriae — deep valleys have been 
subsequently furrowed out through masses of lacustrine and vol- 
canic origin — at a still later date, new cones have been thrown up in 
these valleys — new lakes have been formed by the damming up of 
rivers — and more than one creation of quadrupeds, birds, and plants 
[Miocene, Pliocene, and Post-Pliocene] have followed in succession ; 



* Manual, p. 127, ed. 1855. 



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214 CONCLUDING REMARKS. Chat. IX. 

yet the region has preserved from first to last its geographical iden- 
tity ; and we can still recall to our thoughts its external condition 
and physical structure before these wonderful vicissitudes began, or 
while a part only of the whole had been completed. There was first 
a period when the spacious lakes, of which we still may trace the 
boundaries, lay at the foot of mountains of moderate elevation, 
unbroken lay the bold peaks and precipices of Mont Dor, and una- 
dorned by the picturesque outline of the Puy de Dome, or of the 
volcanic cones and craters now covering the granitic platform. 
During this earlier scene of repose deltas were slowly formed ; beds 
of marl and sand, several hundred feet thick, deposited ; siliceous 
and calcareous rocks precipitated from the waters of mineral springs ; 
shells and insects imbedded, together w^th the remains of the 
crocodile and tortoise ; the eggs and bones of water birds, and the 
skeletons of quadrupeds, some of them belonging to the same genera 
as those entombed in the Eocene gypsum of Paris. To this tranquil 
condition of the surface succeeded the era of volcanic eruptions, 
when the lakes were drained, and when the fertility of the moun- 
tainous district was probably enhanced by the igneous matter 
ejected from below, and poured down upon the more sterile granite. 
During these eruptions, which appear to have taken place after the 
disappearance of the [Lower Miocene] fauna, and partly in the [Plio- 
cene] epoch, the mastodon, rhinoceros, elephant, tapir, hippopotamus, 
together with the ox, various kinds of deer, the bear, hyaena, and 
many beasts of prey ranged the forest, or pastured on the plain, and 
were occasionally overtaken by a fall of burning cinders, or buried 
in flows of mud, such as accompany volcanic eruptions. Lastly, 
these quadrupeds became extinct, and gave place to [Poet-Pliocene] 
mammalia, and these, in their turn, to species now existing. There 
are no signs, during the whole time required for this series of events, 
of the sea having intervened, nor of any denudation which may not 
have been accomplished by currents in the different lakes, or by 
rivers and floods accompanying repeated earthquakes, during which 
the levels of the district have in some places been materially 
modified, and perhaps the whole upraised relatively to the surround- 
ing parte of France.*' 



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APPENDIX. 



CATALOGUE OF ORGANIC REMAINS, 
TABLE OP HEIGHTS, 

AND 

EXPLANATION OF THE 

MAPS AND ENGRAVINGS. 



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APPENDIX. 



ORGANIC REMAINS OF THE TERTIARY AND POST-TERTIARY 
FORMATIONS OF CENTRAL FRANCE. 

Vegetable remains abound in the lower arenaceous beds of the 
lacustrine formations, as well as in the tuffs of the volcanic period, 
where they occasionally form beds of workable lignite. But in 
neither case as yet have they been scientifically determined. They 
chiefly consist of the leaves, fruits, and occasionally stems of dicoty- 
ledonous trees, or of reeds and other plants, the usual growth of 
marshy spots. The stems of chare are very abundant as well as 
their seed-vessels. I am able to say little more of the fossil 
mollusks found in the same formations. The tertiary sandstones 
rarely contain shells, but some species of Cyrena have been found 
in them.* The associated or overlying limestones and marls 
abound in shells belonging to the genera Helix, Lymneus, Paludina, 
Bulimus, Cerithium, Cyrena, Unio, and Cypris. Some of the species 
mentioned by M. Bouilletf appear to be referable to an earlier period 
than that to which, on the best Palasontological authorities, we have 
considered the entire freshwater formation of Central France to 
belong, viz., the Lower Miocene. Sir Charles Lyell has recently 
touched upon this question in a supplement to his Manual.J And 
'the matter remains still open to further investigation. 

Two marine shells are said to have been discovered in a sandy 
stratum near Issoire, by MM. Bravard and Pomel, belonging to 
the genera Natica and Pleurotoma, and akin to some occurring in 
the Faluns of the lower basin of the Loire. Such a circumstance 
would seem to indicate either a reflux at some period of the waters 
of that river, or that the Miocene sea had actually ascended the 



Pomel, Bulletin, 2de Ser., vol. i. t Bull., vol. vi. p. 99 and 255. 

p. 579. | 1857, p. 10. 



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218 



CATALOGUE OF ORGANIC REMAINS. 



Afkbdix. 



Allier. But it is not impossible to account for one or two such 
instances by supposing a few small mollusks living in the lower 
brackish waters to have been brought up the valley by birds prey 
ing on shell-fish. The bones of species belonging to the gull tribe 
are not unfrequent in the Auvergne fresh-water beds. 

The Palaeontologists who have most closely studied the Fauna of 
Central France are MM. Pomel and Aymard. As the lists given 
by these two authorities are not identical, and their opinions vary 
as to the divisions into which the several series should be classed, 
I think my readers will be more satisfied if, instead of myself 
attempting any comparative estimate of the two, I give both cata- 
logues, with an abbreviation of the remarks by which their authors 
accompany them. 

The following is M. Pomel's catalogue of the Fauna of the 
(Miocene) Lacustrine Strata of Central France :* — 

I. — Fauna op the Lacustrine Strata of Central France. 

The species marked * have been found only in the basin of the Haute Loire; 
those marked f have been found both there and in the basin of the Allier 
likewise. Those without any distinguishing mark have been found in the 
latter (the Limagne) basin only. 



Order Cheiroptera. 
Palaeonycteris Robustus 

0. Insectivora. 
Geotrypu8 Acutidens 



MAMMALIA. 



Nob. 



Nob. 



Antiquus .. .. ,, 
Galeoepalax Mygaloides . . . . , , 

My gale Nayadum Pomel 

Plesiosorex Talpoides . . . . Nob. 

Mysarachne Picteti ,, 

Sorex Antiquus ,, 

Ambiguus ,, 

Echinogale Laurillardi .. .. ,, 

Gracilis ,, 

Erinaceu8 Arvernensis .. .. Blainvitte 

Nanus* Aymard.. 



Locality. 
Langy, near St. Gerand-le- 
Puy (Dept. Allier). 

Cournon, Chaufours, near 

Issoire. ' 
Puy de Dome (Coll. Laizer). 
Marcouin, near Vol vie. 
Chaufours, near Issoire. 
Cournon and Chaufours. 
Chaufours. 
Lanjry. 

id. 
Mont Perrier, near Issoire. 
Antoing, near Issoire. 
Cournon and Chaufours. 
Ronzon, near Le Puy. 



• Pomel, Catalogue des Vertebras Fossiles du Bassin Superieur de la Loire, &c. 
Paris. 1854. 



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Appbndix. CATALOGUE OP ORGANIC REMAINS. 219 

0. Bodentia. Locality, 

Pfcla&oeciurus Feignouxi.. .. Nob Langy. 

Chalaniati.. .. , , .... id. 

Steneofiber Escheri , , (Castor) id. and Cbau fours. 

Myoxus Murinus ,, id. 

Myarion Antiquum f .. .. id., Cournon, Chaufours, Le 

Puy. 

Musculoides .. .. Nob Cournon. 

Minutumf ,, Chaufours (Le Puy ?). 

Angustidens .... , , .... id. 

Theridomys Breviceps .. .. Jourd Perrier, Antoign, St. Yvoine. 

Isoptychus Jourdani * .. .. Nob Le Puy. 

Aquatilis* .. .. Aym, .. .. id. 

Vassoni Nob Sauvetat. 

Tseniodus Curvistriatus .. , , .... id. 

Omegadus Echimyoides . . .. , , .... Chaufours. 

Archseomys Arvernensis .. Lai* Vaumas (Dept. Allier), 

Cournon, Chaufours, and 
Langy. 

Palansema Antiquus Nob Cournon and Perignat. 

Lagodus Picoides , , .. .. Langy. 

Amphilagus Antiquus .... , , .. .. " id. Vol vie. 

0. Carnivora. 

Lutrictis Valetoni Pom Langy,. G an net, Gergovia, 

Vaumas. 

Plesiogale Angustifrons .. ,, .... Langy. 

Robusta Ifob id. Vaumas. 

Waterhousii .... ,, .... id. .Cournon. 

Mustelina .... ,, .. .. id. 

Plesictis Robustus ,, .. .. id. 

Gracilis ,, .. .. id. 

Croizeti Pom id. 

Lemanensis .. .. Nob id. 

Genetoides Pom Cournon. 

Palustris Nob Langy. 

Elegans ,, .. .. id. 

Amphictis Antiquus .... ,, .... id. 

Leptorynchus .. ,, .... id. 

Lemanensis .... , , .. .. id. 

Herpestes Antiquus ,, .. .. id. 

Lemanensis .... , , .. .. id. 

Pritnffiva Pom Vaumas. 

Elocyon Martrides* Aym Le Puy. 



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Locality. 


Cynodon Velaunum * .. .. 


Aym. . 


. .. LePuy; 


Palusire* 


» » 


. .. id. 


Canis Brevirostris 


Croizct 


.. .. Gergovia, Langy. 


Amphirynn BrevirOStrJS .. 


Nob. 


.. .. Langy. 


Leptorynchus .. 


1 1 


.. .. id. 


Incertu8 .. .. 


» » 


. .. i<L 


Crapidens .. .. 


Pom. 


.. .. id. 


0. Ungulata. 






Mastodon Tapiroides .. .. 


Cuvier 


.. .. Gannat. 


Deinotberium Giganteum .. 


Kaup. 


.. .. Chaptuzat, Aurillac. 


Cuvieri .. .. 


> f 


.. .. St. Germain Lambron. 


Rhinoceros Lemanensis .. .. 


Nob. 


.. .. Billy, Vichy, Gannat, Chap- 
tuzat, Le Puy, Bournon de 
Sit. Pierre. 


Croizeti 


> > 


. .. Vaumas, Gannat, Bansac. 


Paradoxus .. .. 


> » 


. .. Gannat, Vaumas, Perrier. 


Pabeotheriuni Magnum* .. 


Cuv. 


.. .. Le Puy (Aymard). 


Gracile*.. .. 


Aym. 


.. .. icL * id. 


Velaunumf .. 


Cuv. 


.. .. LePuy, Ronzon, Bournon de 
St. Pierre, near Brioude. 


Duvalii*.. .. 


Nob. 


.. .. Ronzon. 


Plagiolophus Ovinus • .. .. 


> » 


.. .. LePuy. 


Minor* .. .. 


Pom. 


.. .. id. 


Tapirus Porrieri 


> r 


.. .. Vaumas* 


Paheocherus Major 


>» 


.. .. Langy. 


Waterhousii .. 


Nob. 


.. .. Perignat. 


Typus 


Pom. 


id. Langy. 


Suillus 


Nob. 


.. .. langy. 


Elotherium Aymardi . . 


tt • 


.. .. Ronzon. 


Ronzoni .. .. 


-» »- • 


.. .. id. 


Antraootherium Magnum .. 


Cuv. 


.. .. Issoire, Cournon, Chaufoar, 
Vaumas, Digoin. 


Cuvieri.. .. 


Pom. 


.. .. St. Germain Lambron. 


Ancodus Velaunus f -. •• 


Nob. 


.. .. Ronzon, Vaumas. 


Leptoiynchns f .. 


> i 


.. .. id. id. 


Incertusf 


» $ 


.. .. LePuy. 


Aymardi* 


$ > 


.. .. Ronzon. 


Synapbodus Gergovianus .. 


>> - 


.. .. Gergovia. 


Cenotherium Laticurvatum 


Pom. 


.. .. Langy. 


Metopias .. .. 


Nob. 


.. .. id. 


Commune f .. 


Bravard 


Cournon, La Puy, Chaptuzat. 


Elcgans .. .. 


Pom. 


.. .. Langy. 


Leptognatum 


Nob. 


.. .. Chaptuzat, Cournon. 



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Appendix. 



CATALOGUE OP ORGANIC REMAINS. 



221 







Locality. 


Caenotherium Geoflroyi .. .. 


Nob. .. . 


. Langy 


Gracilis .. .. 


Pom. .. . 


. Vanmas. 


Lophiomerix Cbalaniaci .. .. 


Nob. .. . 


. Sauvetat, Cournon, Apt. 


Dremotherium Traguloides .. 


> t .. . 


. Langy. 


Feignouxi .. 


E. Geoff. . 


id., Cournon, Chaufourn. 


Amphitragalas Elegans .. .. 


Pom. .. . 


id. 


Lemanensis .. 


Nob. .. . 


.id. 


Communis*.. 


Aym. . . . 


. Ronzon. 


Boulangeri .. 


Nob. .. . 


. Lanzy. 


Meminoide8.. 


, , .. . 


id. 


Gracilis .. .. 


,, .. . 


.id. 


0. Marsupialia. 






Hyaniodon Leptorynchus f .. 


Tjaxzer .. . 


. Cournon, Sauvetat, Le Puy. 


Laurillardi .. .. 


Nob. .. . 


. Antoing, near Issoire. 


Didelphis Arvernensis f . . • • 


Qerv. .. . 


. Langy, Cournon, Sauvetat, 
Le Puy. 


Crassa* 


Agm. .. . 


. LePuy. 


Antiqua 


Nob. .. . 


. Cournon. 


Lemanensis .. .. 


ii •• • 


. Sauvetat. 


Minuta* 


Aym. .. . 


. LePuy. 



AVES. 

M. Pomel leaves the numerous remains of birds found in this 
district undetermined, mentioning only the genera Phsenicopterus, 
Anas, Ardea, and one resembling Numenius, several of the orders 
Rapaoes, and Gallinacei, one of the last being as large as a peacock. 



REPTTLIA. 



0. Chelonia. 



Testudo Hypsonota Nob. 

Lemanensis Brav. 

Ptychogaster Heckei .. .. Nob. 

Emydoides .. Pom. 

Abbreviata Nob. 
Chelydra Meilheuratias .. .. ,, 

Trionyx Geoff. 



Langy, Bournouele. 

id. Cournon. 

id. Chaptuzat 

id. 

id. 
Vanmas, Chaufours. 

id. Chignat. 



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222 CATALOGUE OF OBGAKTC BEMAIKSL Attitocl M 


O.Sa*n*. 




Jjootnty, ^H 


DiplocTDodtts Rjttelii f .. 


Pom. .. .. 


Ronnon, Langy, Cha$>tiiza% 
Perrier, A filming Stowtax. 


Vartnos Lemuenns 


.. Xcb. .. .. 


Chaafoars. 


Dracsrooauiras Cruized .. 


*• 9 » .... 


Cootdckl. 


SaoitHDoruf Ambijmas .. 


.. , , .... 


Lan^y, Maroouia, near Vohrie. 


Laoertinas .. 


»» 


kL 


Lacerta Antiqua .. .. 


»» .. 


Cootdod. 


0. Ophidia. 






Ophidioo Antiques .. .. 


Aofc, .. .. 


Langy. 


0. Bairachia, 






Batrachns Lemanensis .. 


.. Nob. .. .. 


Langy, Coarnon, Chaaibma. 


Xayadum 


» t •• •• 


Chaufours. 


Lacuatris 


9 , .. •• 


id. 


Protopbrynus Aretbuaa .. 


.. M •• •• 


id. 


Cbelotriton Paradoxus .. 


»» •• •* 


id. Langy. 




PISCES. 




0. CUrurides. 






Perca Lepidota 


.. Agamiz .. .. 


Vichy, Gergoria. 


0. Cydoides. 






Cobitopsis Exilis 


.. Ato 


Chadrat, near St. Anwid 


Lebiaa CephalotU .. .. 


.. Agau 


Corent. 


Perpusilus .. .. 


>» .. .. 


Laps. 



It appears from this list that the Fauna of the Miocene lacustrine 
strata, known to M. Pomel, comprehends the following number of 
species : — Cheiroptera, 1 ; Insectivora, 12 ; Bodentia, 18 ; Carnivora, 
27 ; Ungulata, 42 ; Marsupialia, 7 ; Chelonians, 7 ; Saurians, 6 ; 
Ophidians, 1; Batracians, 5; Fish, 4: in all 130 species, besides 
several of birds as yet undetermined. Twelve species out of this 
number are found in the basin of Le Puy only; and eight are 
common to the basins of the Allier and the Loire (i. e . the Limagne 
and of Le Puy). Some of the most characteristic species, as, for 
example, all those which belong to the locality of Vaumas (Dept 
Allier, not far from the confluence of the two rivers, Allier and 



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Appendix. 



CATALOGUE OF OBGANIC REMAIN8. 



223 



Xiorre), comprehending Ancodus, Antraeotherium, Tapir, Rhinoceros, 
and Chelydra, associated with Archemys, Amphictis, Herpestes, Am- 
phfcyon, Caenotherium, Testudo, and Crocodilns, occur in the sands 
and sandstones which form the lowest beds of the lacustrine series. 
On the other hand, the locality of Langy, near St. Gerard-le-Puy 
(Dept Allier), so rich in Cheiroptera, Insectivora, Rodentia, Car- 
nivora, Ungulata, as also in birds, Saurians, Tortoises, Laeerto, 
Ophidia, and Batracia, belongs to the Indusial limestone, which 
generally appears in the upper beds of the series Chaptuzat, Mar- 
louis, and Gannat in the Puy de Dome are in the same position. 

From these and other observations, M. Pomel concludes that the 
entire series of lacustrine beds of the two basins belong to the same 
Geological and Zoological period, and cannot be distinguished 
chronologically by their Palseontological characters ; the same species 
being found in the most recent as in the most ancient beds of the 
series ; and whatever differences exist being capable of reference to 
accidents of distribution or of discovery. 

Comparing this Fauna with those of other European tertiary 
districts, M. Pomel finds it to bear the strongest analogy to that of 
Mayence, and he classes it therefore as earlier than the Falunian 
(Upper Miocene), and more recent than the Parisian Gypseous 
deposits (Eocene). This would establish it as of the "Lower 
Miocene" period, which in fact is the position, as already stated, 
assigned to it by Sir C. Lyell. 



II. — Pliocene Fauna, of the Volcanic Mvla of Central France. 

(Tuffs and Breccuts of Mont Perrier, Cussac and Vtolette, (JIaute Loire,) $c. 



0. Bodentia. 

Castor Issiodorensis 
Arvioola Robustus 

(?) 
Hystrix (?) 
Lepra Lacostii 



MAMMALIA. 

Locality, 

Croizet Pumiceous Tuff of Perrier. 

Nob ill. 

id. 

Croizet id. 

Nob. id. 



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Z24 (JATALUli 
0. Carnivora. 


U15 CUT UKUAflU 


Locality. 


Ureas Arvernensis .. .. 


Croiz. and Joberi 


Pumiceoua Tuff of Pemcr. 


Lutra Bravardii 


Pom 


id. 


Mustelina 


Nob 


id. 


Zorilla Antiqua 


(RabdogdU Nob.) 


id. 


Felis Arvernensis 


Croiz. and Job. 


id. 


Pardinensis 


> » 


id. 


Brachyryncha .. .. 


> > 


id. 


Issiodorensis 


9 9 


id. 


Brevirostris 


9 9 


id. 


Inoerta 


Pom 


id. 


Meganthereon Oultridens 


Nob 


Under Basalt at Sainzelles* 
near Polignac 


Macroscelis 


Brav 


Tuff of Perrier. 


Hyaena Perrierii 


Croiz. and Job. 


id. 


Arvernensis .. .. 


9 9 


i<L 


Dubia 


9 9 


id. 


Vialetti* 


Aymard .. .. 


Vialette (Haute Loire). 


Canis Megamastoides 


Pom 


Tuff of Perrier. 


0. Ungulata. 






Mastodon Arvernensis f .. 


Croiz. and Job. 


Tuff of Perrier, Vialette, 
Mirabelle (Ardeche)i 


Borsonif .. .. 


Kays 


Tuff of Perrier, Vialette, Le 


(M. Veilavus, 


Aym.) 


Puy. 


Rhinoceros Elatus .. .. 


Croiz. and Job. 


Mont Perrier. 


Tapirus Arvernensis .. .. 


9 9 


id. 


Sub Arvernensis 


9 9 


id. 


Cervns Boberti • 


Job 


Polignac, near Le Puy. 


Perrierii 


Croiz. and Job. 


Tuff of Mont Perrier. 


Issiodorensis .. .. 


9 9 


id. 


Etueriartim . . . . 


9 9 


id. 


Pardinensis .. .. 


9 9 


id. 


Rusoides 


Nob 


id. 


Aniens 


Croiz. and Job. 


id. 


Cladocerus .. .. 


Nob 


id. 


Ramosus 


Croiz. and Job. 


id. 


Solilhacus* .. .. 


F. Robert .. .. 


Solilhac, near Le Puy. 


Cusanns 


Croiz. and Job. 


Mont Perrier. 


Leptoceros .. .. 


Nob 


id. 


Platyceros 


> > 


id. 


Furcifer 


>> .. .. .. 


id. 


An ti lope Antiqua .. .. 


> » 


id. 


Bos Elatus 


Croiz 


id. 


Elaphus 


Nob 


id. 



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Appendix. CATALOGUE OF ORGANIC REMAINS. 226 

The Fauna of the Pliocene period thus contains of Eodentia 5, 
Carnivora 17, Ungulata 23 species : in all, 45. Neither Chelonians 
nor Saurians have been hitherto discovered in it The lakes had 
been evidently drained. 

It will be observed that this Pliocene Fauna is almost wholly 
confined to the tufaceous conglomerates of one locality, that of 
Mont Perrier near Issoire.* Sir Charles Lyell's paper on the sub- 
ject of this remarkable deposit, read before the Geological Society, 
November 19, 1845, will be well known to my readers. The fresh- 
water strata and the overlying sheets of basaltic lava had evidently 
been eaten into by deep valleys before the deposition of these 
tuffs, and the gravel beds on which they rest. Sir C. Lyell dis- 
tinguishes two distinct beds containing bones interstratified with 
the tuffs. Subsequently to this eluvial accumulation of trass-like 
tuffs from the Mont Dore new valleys appear to have been excavated 
through them, in which newer ossiferous alluvial deposits occur. 
And it is to these alluvial beds that a large part of the following 
(Post-Ptiocene) Fauna from M. Pomel's catalogue belongs. 

M. Pomel observes that the most striking characters of the 
Pliocene Fauna given above are the large assemblage of Cervi, the 
number of large Felis, of which one, the Megan thereon, is, besides the 
Mastodon, the only extinct genus of this Fauna. The Rodentia are 
of European genera. The Ungulata comprehend Mastodon, rhinoceros, 
tapir, sus, cervus, antelope, and bos. The elephant, hippopotamus, 
and horse are absent. M. Pomel considers this deposit as of the 
age of the Subapennine tertiary strata. 



FISH OF THE BASIN OF MENAT.— Qii. POST-PLIOCENE? 

Perca Augusta .. .. .. Jgassiz. 

Gyclurus Valenciensii .. .. , , 

Pa?cilop8 Breviceps .. .. Nob. 

Esox . . . ? 



See page 135. 



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226 



CATALOGUE OF ORGANIC REMAINS. 



Amarus. 



in. — Fauna op Ancient Alluvia (Po6t-Puocene). 

This series (as will be seen below) combines two or more distinct 
periods. 

Sir C. Lyell, indeed, distinguishes these alluvia in the neigh- 
bourhood of Issoire into four successive divisions (Nos. 6, 7, 8, 9, of 
his section. — Manual, ed. 1855, p. 552.) 

MAMMATJA- 
0. Insect ivor a. Locality. 

Talpa Fossilis Nob Bone Breccia of Condes near 

Issoire and Neschers. 

Sorex Exilis ,, .. .. id. 

Fossilis , , .. .. id. 

Myosictis Fodiens Pom id. 

Musaraneus Prisons Nob id. 

Erinaccus Major Pom Alluvium at Peyrolles near 

Issoire. 

0. Rodentia. 

Sciurus Ambiguus Nob In crevices of Lava of Grave- 

neire. 
Spermophilus Superciliosus .. Kaup. .. Paix near Issoire, Coudes, and 

Neschers. 

Arctomys Lecoq Nob Champeix, Ch&telperioux, and 

ere vices of Lava of Graveneire. 

Castor Faber? Lin Near Clermont. 

Myoxus Nitella? ,, .. .. Coudes. 

Arvicola Antiquus Nob id. Neschers, Langy. 

Pseudoglareolus .. Pom Coudes. 

Arvaloides .. .. Nob id. Neschers, Sec. 

Joberti ,, .. .. Coudes. 

Lemmus Fossilis. 

Mus Sylvaticus Lin id. 

Cricetus Musculus Nob id. 

Lagomys Spelams? Omen.. .. id. 

Lepus Diluvianus? Pietet.. .. id. Aubiere, Champeix, 

Neschers, Chatelperron. 
Cuniculi Affiais .. .. .. .. id. 

0. Carnioora. 

Ursus Spelaous Blum. .. Caves of Chatelperron, Cham- 
peix, and Montaigu le Beilin. 



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Appendix. 



CATALOGUE OF ORGANIC REMAINS. 



227 



Meles Fossilis Auct 

Mustek Schmarlingii .. .. Nob 

Putoriii9 Fossilis Auct 

Gale Nob 

Microgale ,, .. ,. 

Macrossonia .... , , .. .. 

Felis Lyncoides ,, .. .. 

Minuta ,, .. .. 

Spebea Gold/. .. 

Meganthereon Latidena * .. Nob 

Canis Spelasus Gold/. 

Neschersenfiis Croiz. 

Vulpes Fossilis .. .. Auct. 

Hyaena Spelaeaf Goldf. .. 

Brevirostrisf Aym 

0. UnguUita. 

Elephas Meridionalis .. .. Blum. 

Primigenius .. .. Nesti .. .. 

Priscua Gold/. 

Rhinoceros Leptorhinus .. .. Cuv 

Aymardi* .. .. Ifob. .. .. 

Theiorinus .... ,, .. .. 

Equus Adamiticus SM 

Robustus Nob. .. ., 

Tapirus Elegans t >, .. . 

Sua Priscus M.Serres. 

Hippopotamus Major f .. .. Cuv. .. . 

Cervus Guettardi f , , .. . 

Somonensis ,, .. . 

Intermedins f .. .. M.Serres. 



Macroglochis 
Ambiguns . 



Nob. .. 



Locality. 

Caves of Chatelperron, Cham- 
peix, and Montaigu le Bell in. 

Coudes, Aubieres, Neschers. 
id. 
id. 

id. Neschers. 
id. 

id. Tour le Boulade. 
id. Aubieres. 

Montaigu Cavern. 

Sainzelles, Haute Loire. 

Coudes, Tour de Boulade, Mon- 
taigu. 

Neschers. 
id. Coudes, Aubiere, Cha- 
telperron, Sainzelles? 

Scoria of St. Privat d'Allier 
(Haute Loire). 

Sainzelles, Ardes near Issoire. 



Tour de Boulade, Vichy, &c. 

Malbattu, Clermont, Le Puy, &c 

Plain of Sarlieve. 

Peyrolles near Issoire, Malbattu. 

Under Basalt (Haute Loire). 

Tour de Boulade, Vichy, Chatel- 
perron. 

Paix, Boulade, Coudes, Neschers, 
Gergovia, Le Puy, &c. 

Champeix, Malbattu, Peyrolles, 
upper beds of Perrier. 

Le Puy, Tonneil. 

Coudes, Boulade, Montaigu, Cha- 
telperron caverns, &c. 

St. Yvoine, Tormeil, Montaigu, 
Sainzelle near Le Puy. 

Boulade, Nerchers, Coudes, St. 
Yvoine, Chatelperron. 

Gergovia. 

Boulade, Champeix, Chatelper- 
ron, Scoria of St. Privat, at 
LeGard. 

Peyrolles near Issoire. 
id. 

Q 2 



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228 CATALOGUE OF ORGANIC REMAINS. Apfetouu 

Locality. 

Antilope Aymardi * Nob Boulade, Le Puy. 

Incerta ,, .. .. Coudes. 

Ovis Priraoeva Oerv Coudes, Chatelperron. 

Capra Rozeti Pom Malbattu. 

Bos Primigenius t Blum. .. Boulade, Cbampeix, Aubteres, 

Vichy, Chatelperron. 

Giganteus* (Vdaunusf) Cussac. 

Priscusf Schht. .. Peyrolles, Tormeii, Anciat. 

0. Kept ilia. 

Laoerta Fossilis Nob Neschers. 

Coluber Gervasii ,, .. .. Coudes. 

Fossilis ,, .. .. id. 

Rana Fossilis ,, .. .. id. 

It has been already mentioned that M. Pomel refers this Alluvial 
Fauna to two distinct periods, the earliest of which is characterised 
by exclusively containing the following species : — Erinaceus Major, 
Ursus Spelceus (Xeschersensis, Croizet), Hycena Brevirostris, Cams Nes- 
chersensis, Elephas Meridionalis, Rhinoceros Leptorhinus, i?. Aymardi, 
Meganthereon latidens, Tapirus, .... ? Equus s Robust us, Hippopotamus 
Major, Cervus Ambiguus, C. Macroglochis, Capra Rozeti, Bos Prisons. The 
other species in the catalogue are for the most part common to these 
earlier, and to several later alluvial deposits, occurring either in the 
plain of the Allier at no great height above its present level, or in 
taluses leaning against the sides of existing valleys, or in gravel beds 
supporting the more recent lava currents, or in caves and fissures of 
these or the older rocks. M. Pomel does not recognise any dis- 
tinction of age founded on Palaeontological evidence between these 
different last-mentioned deposits. 

The greater number of genera represented in them are still found 
in France, and perhaps some of the species. Those not now existing 
in the country are spermopMus, arctomys, lemur, cricetus, lagomys, ursus, 
hyaena, ekplias, rhinoceros, antilope. But even of these many species are 
still to be found in Europe. He remarks as singular that together with 
the elephant, rhinoceros, and hycena, which recall a warmer climate 
than that of France in the present day, occur marmots, lemmings, 
bears, and others now for the most part inhabiting Alpine or colder 
climates. And he observes in explanation of this, that the molars 
of the herbivorous animals of this Fauna show marks of their having 



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Appbkdix. CATALOGUE OF ORGANIC REMAINS. 229 

largely fed upon coniferous plants, leading to the opinion that this 
district in their time possessed a climate colder than the actual one. 

This Fauna is in fact almost identical with that of the older 
superficial alluvia or drift of the entire surface of Europe. 

I have already shown that, in company with this last-mentioned 
group of species now extinct, human remains have been discovered 
in the volcanio tuff of Le Puy. 

M. Aymard, Vice-President of the Academio Society of Le Puy, 
and a naturalist who has attentively studied the Geology and 
Palaeontology of the Haute Loire, and possesses a very rich collec- 
tion of its fossils, classes the tertiary formation of that district in the 
following manner : * — 

1. Lower Eocene. — Variegated clays and marls of Le Puy, Em- 
blaves, and Brioude. 

2. Upper Eocene. — Gypseous marls and clays of the basin of Le 
Puy. 

3. Lower Miocene. — .Calcareous marls — siliceous limestone, and 
sand beds of the basins of Le Puy and Brioude, St. Pierre 
Eynac, Mathias near Fay-le-froid, &c. <&c. 

4. Pliocene — comprehending three successive series of Alluvial 

deposits, all underlying the volcanic rocks, viz. A. 
the inferior sand beds of Vialette, Pioheviel, Taulhac, 
Laroche near Vals, Coupet, <fcc. B. Intermediate alluvial 
beds and stratified breccias of Sainzelle, near Polignac, <fcc. 
C. Upper alluvia and breccias, tuffs, <fcc, of Solilhac, Polignac, 
Le Collet, Estronilhas, St Privat d'Allier, Chilhac, Mon- 
tredon, Cussac, Les Trois Pierres, Corsac near Brives, &c. 

5. Post-pliocene or superficial alluvia and volcanic stratified 

breccias, ossiferous fissures, detritus, <fec, of Denise, Croix- 
de-la-Paille, Malpas near Aiguille, &c. 

The organic remains contained in these divisions, according to 
M. Aymard, are as follows : — 

No. 1. — A few herbaceous plants, no trace of animals, except 
perhaps some bones of the Palceotherium Primcevum. 



* In a paper read by him before the 13th Sept. 1855. See the Report, vol. 
Scientific Congress of France at Le Puy, i. p. 228. 



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230 CATALOGUE OF ORGANIC REMAINS. ArnexnoL 

No. 2. — Two species of mammalia, viz., PaUsotherium StAgradU y 
Aym., and Monacrum Vdaunum, Ay in., the eggs of some large aquatic 
bird, impressions of small fish, one crustacean ElesQphus (mums, 
and a few freshwater mollusks, lymnei, paludinas, planorbes, and 
cyclades. 

No. 3 is much richer in fossils, a single bed at Honzon net* 
Le Puy containing the greater part of the following list of 
new species all named by himself. Insectiwra : — Tetracus Nanus* 
Carmvora : — Cynodon Velaunus, 0. Palustris, Elocion Martrides. 
Rodentia: — Theridomys Aquatilis and T. Jpurdani, Myoterium 
Minutum, M. Aniciense, Decticus Antiquus, Elomys Prisons. 
Pachyderms : — Ronzotherium Yelaunum, E. Cuvierii, Patootherium 
Gervaisii, Paloplotherium Ovinum, Entelodon Magnus, E. Ronzoni, 
Bothriodon Platorynchus, B. Leptorynchus, B. Velaunus, Zooligus 
Picteti, Gelocus Communis, G. Minor, Palaeon Riparium, Lathonus 
Vallensis. Ruminants : — Orotherium Ligeris. Subdiddphis : — Hyaano- 
don Leptorynchus of Laizer. Didelphis : — Peratherium 'Elegans, P. 
Crassum, P. Minutum. Of Birds he recognises the remains of 15 
species not well determined as yet, chiefly aquatic, Buch as cranes, 
flamingoes, plovers, gulls, with some of the order of Rapaces. 
Of Reptiles several Chelonia, Chersites, Elodites, and perhaps 
Potamites; several large and small Saurians, and more than one 
Batracian. Of Fish one only species, small but very numerous, 
Pachystelus Gregatus, Aym. Of Insects, 2 species of Coleoptera, 
and several belonging to marsh-frequenting genera. Two species of 
Crustacea, Elosilphus Limosus and Cypris Faba ; several Palustrine 
mollusks, of the genera Lymneus, Planorbis, Helix, Cyclas, Ac. ; 
Infusoria, and numerous impressions of the leaves of dicotyledonous 
and leguminous plants, Comptonia, and Chara (Gyrogonites). 

There appears on examination of these catalogues scarcely suffi- 
cient Palaeontological ground for the triple division of the lacustrine 
formation which M. Aymard suggests ; and it would seem more 
reasonable to refer the whole to a single period — the Lower Miocene, 
as is done by M. Pomel and Sir Charles Lyell. 

Again, M. Aymard's division of his 4th class into three series 
seems an equally unnecessary complication. It corresponds to the 
Pliocene or older Alluvia of Pomel and Lyell. M. Aymard's 



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Appendix. CATALOGUE OP ORGANIC REMAINS. 231 

observations on the character of its organic remains are valuable 
from his intimate acquaintance with the localities. They are all 
what he calls sub- volcanic, that is, contemporaneous with the vol- 
canic products of the district, generally interstratified with the 
basaltic plateaux, or their underlying tuffs and breccias. A com- 
plete break separates the Palaeontology of these Pliocene alluvia 
from that of the Lacustrine strata already described. They contain 
noarcely any of the genera, and not one of the species, hitherto found 
in any part of the last-mentioned formation. And it is not unrea- 
sonable to refer this great change to the occurrence in the interval 
of the earlier volcanic convulsions, and the consequent drainage 
and partial excavation of the lacustrine beds. New races of beings 
had succeeded to those in existence during the Lacustrine period, 
and many of them continued to inhabit the district even after the 
extinction of the most recent volcanos. The Flora of the volcanic 
period is represented chiefly by impressions of leaves and fruit 
belonging to trees still growing in the neighbourhood. The same 
may be said of its Fauna, so far as respects Mollusks, Insects, and 
Batracians. The Mammalia alone exhibit a very decided difference 
from those of the present age. It contains at least three species 
of mastodons,* a machairodus, a tapir, hyaenas, a rhinoceros, ele- 
phants, hippopotamus, besides several extinct species of Canis, 
Cervus, Antilope, Bos, Equus, and Sus. 

M. Aymard's 5th class, the Post-pliocene superficial alluvia, 
ossiferous fissures, &c., agrees with the parallel division of M. 
PomeL Its Fauna is characterised by the first appearance of the 
Bear, and some small extinct species of Cervus, and also comprises 
some extinct species of elephant, rhinoceros, horses, and cervus, 
identical with those occurring in the earlier series. Man likewise 
(as we have seen) appears to have been an inhabitant of this dis- 
trict before the complete termination of this last volcanic period. 



* One found at Vialette, Mastodon Vellavus, Aym., U larger by one-third than 
the M. OiganteuB of Cuvier. 



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TABLE OF HEIGHTS 



IN THE 



VOLCANIC DISTRICT OF CENTRAL FRANCE. 



[N.B. The greater number of these heights are extracted from Bamond's 
NiveUement BaromStriqm des Monts Dore et D6me ; the remainder are 
derived from articles in the Journal des Mines, by M. Cordier, &c, and from 
the work of M. Bertrand Roux.] 

Puy de Sancy, Monts Dore Trachyte 

Plomb du Cantal .. .. Clinkstone 

Le Mezen, Haute Loire Clinkstone 

Col de Cabre, Cantal Clinkstone 

Le Mont Lozere Mica-slate 

Le Puy Man, Cantal Clinkstone 

Pierre-sur-Haute, Forez Granite 

Le Puy Violan, Cantal Clinkstone 

Puy Gros, n. of Baths, Monts Dore .. Trachyte 

Puy de Dome Trachyte 

Croix Morand Plateau Basalt 

Source of the Loire, Haute Loire .. .. Clinkstone 
Estables, village, Haute Loire .. .. Granite 
Road from Le Puy to Pradelles, Haute Loire Basalt on granite 
Puy de Laschamp, Monts Dome .. .. Scoriae 
Petit Puy de Ddme, Monte Ddme .. .. Scoria? 

Puy de Come, Monts Dome Scoriae 

Puy de Pariou, Monts Ddme Scoriae 

Puy de Cliersou, Monts Ddme .. .. Trachyte 
Puy du Petit Suchet, Monts D6me . . Scorias 
Puy de Louchadiere, Monts Dome . . . . Scoria) 
Puy de Las Solas, Monts Ddme .. .. Scoria) 

Lac Paven, Monte Dore Basalt 

Puy de Mont-char, Monts Dome .. .. Scoriae 
Puy de Chopinc, Monts Ddme . . Trachyte 





Eng.fc«t 

abore 
the Sea. 


.. Ramond 


6217 


»» 


6096 


. . Cordier 


6820 


• • . •• *> 


5545 


„ 


5535 


„ 


5444 


.. Bamond 


5409 


» 


5228 


,, 


5040 


,, 


4842 


,, 


4703 


.. .. B. Boux 


4593 


„ 


4436 


pranite „ 


4203 


.. Bamond 


4196 


„ 


4187 


i» 


4173 


»» 


4012 


» 


3992 


„ 


3983 


»♦ 


3956 


• • »* 


3950 


„ 


3943 


♦* 


3933 


,, 


3910 



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Appendix. 



TABLE OF HEIGHTS. 



233 



Puy de Jume, Monts D6me 

Pey-Veuy, Haute Loire, near Montbonnet 

Montagne de Bar, Haute Laire 

Grand Sarcoui, Monts Dome .. 

Puy des Goules, Monts Ddme 

Puy des Montgy, Monts D6me 

TSte de la Serre, Monts Dome 

Puy de Chatrat, Monts Dome 

Puy de Manson, Monts Dome . . 

Puy de St. Sandoux, Monts Dome 

Puy Girou, Monts Ddme 

Puy Barnere, Monts Dome .. 



Orcines, village, Monts D6me . . 
Graveneire, Monts Ddme 
Prudelles, Monts Dome .. 
Cotes de Clermont^ Monts Ddme 



Puy de Dal let, near Pont du Chateau .. 



Threshold of Hotel de Ville at Le Puy .. 

Puy de Crouel, Limagne 

Clermont, Place de Jaude, Puy de Dome 
Level of the Allier at Pont du Chateau .. 



Scoria 

Scoria* 

Scoriae 

Trachyte .. 

Scoria 

ScoriaB 

Basalt on granite 

Basalt on granite 

Basalt on granite 

Basalt on granite 

Basalt on fresh- 
water marly 
limestone. 

Basalt on fresh- 
water marly 
limestone. 

Granite 

Scoria* 

Basalt on granite 

Basalt on fresh- 
water marly 
limestone. 

Basalt on fresh- 
water marly 
limestone. 

Calc peperino . . 



Eng.feet 
above 
the Sea. 

Ramond 3848 

B. Roux 3822 

3816 

Ramond 3799 

3796 

„ * 3792 

3461 

3372 

3310 

2821 

2792 



2780 



2779 
2723 
2313 

2089 



2007 

B. Roux 1710 
1430 
1286 
1026 



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EXPLANATION 



or THE 



MAPS AND ENGRAVINGS 

ILLUSTRATIVE OF THIS MEMOIR 



MAPS. 

No. 1. 

•• The Volcanic District of Central France." 

Comprising the greater part of the primary platform, and contain- 
ing tlio department* Pay de Ddme, Loire, Rhone, Haute Loire, Cantaly 
Ardwfui, htzfor % and parts of the Aveyron, Correze, Creuse, and After. 
The area* occupied by the volcanic products are distinguished in 
colour*, as well as those of the principal crystalline and sedi- 
mentary formations, and the several coal-basins. This map is 
copied for the most part from the * Carte Geographique de la France/ 
omitting the subdivisions, which would have been too complicated 
for the scale employed. 



No. 2. 

11 The Month Dome and Part of the Limagne." 

Kxhibiting tho chain of puys rising from the granitic platform 
lirhtoh fTOpantts tho Allier and Sioule. The extent of surface 
BbTHttK) hy tin voloanic cones and their lava-currents is indicated 
i uttlotm*, us well as the limits of the primary and freshwater 
formations, utid the more ancient basaltic currents which have 
ffowtd frost lht< MontDore in that direction. 



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EXPLANATION 



OF THE 



MAPS AND EXGEAVINGS 

ILLUSTRATIVE OF THIS MEMOIR 



MAPS. 

No. 1. 

44 The Volcanic District of Central France." 

Comprising the greater part of the primary platform, and contain- 
ing the departments Pay de Dame, Loire, Rhone, Haute Loire, CantaL, 
Ardeche, Lozert, and parts of the Aveyron, Correze, Creuse, and AUier. 
The areas occupied by the volcanic products are distinguished in 
colours, as well as those of the principal crystalline and sedi- 
mentary formations, and the several coal-basins. This map is 
copied for the most part from the 4 Carte Geographique de la France,' 
omitting the subdivisions, which would have been too complicated 
for the scale employed. 



No. 2. 

44 The Monts Dome and Part of the Limagne." 

Exhibiting the chain of puys rising from the granitic platform 
which separates the Allier and Sioule. The extent of surface 
covered by the volcanic cones and their lava-currents is indicated 
by colours, as well as the limits of the primary and freshwater 
formations, and the more ancient basaltic currents which have 
flowed from the Mont Do re in that direction. 



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CPLANATION OF THE PLATES. 285 



Plate L 



dw of the Environs of Clermont, taken from the 

uy Girou, a conical peak of columnar basalt, about 

h of that town. The chain of puys of the Monte 

to the west, with the Puy de Ddme in the centre, 

a surface of the granitio platform. To the north lies 

Jlermont, eaten out of the freshwater formation, and 

t the primary escarpment, on the edge of which rises 

Icanio cone of Graveneire. Beyond Clermont are seen 

platforms of Les Cdtes and Chanturgues ; in front, a 

Jc crowned by the Castle of Montrognon. Eastwards, 

the village of Opme, rise the Puy de Jussat and the 

Gergovia, both in all probability once continuous with 

of Girou. To the south is seen in its whole extent the 

platform of La Serre, partly resting on granite, partly on 

rwater marls, and terminating at the village of Le Crest. 

it rise the tracbytic heights of the Mont Dore, and its 

embranchments ; with the insulated basaltic plateaux or 

S St Sandoux, St Saturnin, Coran, Monton, <fcc. 

horizon is closed by the mountains of the department of the 

I Loire. Immediately below these distant heights the valley 

f Allier appears narrowed by the quantity of basalt which, has 

d in that direction from the vicinity of the Mont Dore. Beyond 

river rises an insulated group of hills capped by basalt and 

Ay composed of freshwater limestone, but partly of granite and 

tidary sandstone. They are called the Puys de Millefleur, 

Bomain, Mauriac, Dallet, <fec. At the foot of this range flows 

i Allier, and immediately enters the wider expanse of the Limagne 

Auvergne, which, bounded only eastwards by the distant granite 

nge of the Forez, stretches to the horizon on the north-east of 

le station. The cone of Graveneire, and the lava-current bursting 

rom its side and spreading thence over a large surface of the 

jwor plain, are remarkable objects to the north of the spectator. 



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236 



EXPLANATION OF THE PLATES. 



Plate II. 

Distant View of the Chain of Puys, or Monts Dome, taken 
remnant of basalt crowning the western bank of the Sionle, a 
distance below Pont Gibaud. Nearly all the cones are visible ; 
most conspicuous are those of Louchadiere and Come. The Us 
streams poured forth by these two vents may be seen spreading* i 
broad sheets from the base of the cones over a wide extent of t 
granitic platform, and uniting immediately above the Castle 
Pont Gibaud to pour over the banks of the valley of the Sioule 
spreading sheet, which is, however, partly hidden by forest 
underwood. That part of the lava-current which occupies 
former bed of the Sioule is, on the contrary, still bare and rug 
its surface appearing like a series of heaps of loose basaltic bk 
Between this and the granite cliffs to the right, the river dashsl 
and foams through the narrow channel it has excavated by under*! 
mining the granite. At the angle immediately beneath the i 
the basalt exhibits a regularly columnar structure. 

In the distance to the right is the outline of the central trachj 
eminences and plateaux of the Mont Dore, from amongst which tb* J 
Sioule takes its rise. 



Plate III. 

Transversal View of the Northern Chain of Puys, from the 
Summit of the Puy Chopine. The cone of La Goutte, which half 
encircles the Puy Chopine, forms the foreground. The Puy de Come 
and the commencement of its lava-current are seen to the extreme 
right. The Puys de Dome, Cliersou, Suchets, Pariou, with the 
beginning of its lava-stream, <fcc., in the front ; and the group of 
Les Goules and the Sarcouis, with the Puy Chaumont, on ihe left. 
The Mont Dore and the mountains of the For&z and Haute Loire, 
tikirt the horizon to the right and left. The observer looks due 
Mouth. 




Gruiuultail*. 

man. 
Houtettte, 




I V> t'JU»N THE WKS1 



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i 



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^ofcgle 



*t. l+uy 
u. ivm 



- 



,■ Mwtl I' ■• 



Plate III. 



■. I ('.Mlllll'i 








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I 



238 EXPLANATION OF THE PLATES. M 

the Castle of Montredon, built upon an insulated peak of \x 
once continuous with the former. To the right are the 1 
Combe-grasse, La Taupe, Montgy, Pourcharet, Mxmtjaghat 
Monchal. At the foot of the last stands the farm of 31. le Cm 
Mo/dosier, author of * Essai sur les Volcans d'Auvergne/ "who 
blished himself in the midst of this volcanic desert, and am 
in turning its arid plain of scoriae into productive corn -land ; 
notwithstanding the great elevation of the spot, it la compk 
sheltered by the encircling range of volcanic cones, and the ft 
of the soil is unquestionable. Here he died in 1840, and here 
buried ; the influence of the Jesuits, whose intrigues lie 
in his admirable political writings, having prevented his int 
in any consecrated burial-ground. 



Plate VL 

Valley of Villar, and Plateau de Prudelle on the summit of 
granite slope to the left. Below a Roman paved road is based 
i ho comparatively recent lava-current of Pariou. The ravine to 
right has been excavated since the flow of this lava through 
granite bank to the right. 



Plate VII. 



< 



This general sketch of the Mont Dore is taken from the foot a 
the Puy GVos, whence a bird's-eye view is obtained of the Valley « 
the Dordogne, in which lies the village of the Baths. At its npp* 
extremity is the deep circus which appears to have been the site « 
the chief vent of the volcano. The principal peaks which enmrck 
this gorge are named in the references. From those called the R* 
de Cuzau on the left, and Le Cliergue on the right, wide platfonni 
of trachyte slope gradually towards the observer. The first fofl« 
the Plateaux de Durbise and de Langle ; they may be seen in ti* 
motions afforded by the valley of the Baths to rest upon tuffc 

is again on a parallel bed of olinkstone, and this on basalt with 






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Appendix. EXPLANATION OF THE PLATES. 289 

the interposition of conglomerate. At the Cascade du Mont Dore, 
immediately above the Baths, this superposition is very evident. 
The Plateau de Bigolet, on the other side of the valley, is simi- 
larly constituted, as may be seen in the valley of La Scie on 
its opposite side. By this it is separated from another extensive 
embranchment consisting of repeated beds of trachyte, and forming 
the Plateau de Bozat, from beneath which basalt crops out at the 
Plaine de Chamablanc. The similarity in height, slope, and struc- 
ture of the Plateaux de Langle and Bigolet leads to the opinion that 
they were once continuous. Their separation may have been 
effected by a local earthquake, and enlarged by the erosion of the 
river. The left of the field of view is occupied by a series of 
swelling trachytic eminences, of which it is difficult to determine 
whether they were thrown up in their present irregular and rounded 
forms, like the trachytic puys of the Monts D6me, or produced by 
the unequal weathering of a massive hummock. Basalt appears to 
crop out also from beneath these trachytes on the north- east side ; 
but from the quantity of debris of trachyte accumulated along the 
lines of junction, it is difficult to find any positive fact of super- 
position. The Puys de Loueire and Trioulerou, at the extreme left, 
are of very slaty trachyte (clinkstone), a variety which predomi- 
nates in that direction. 



Plate VIII. 



View towards the north, from near the Puy Gros, looking down 
one of the tributary valleys of the Sioule, towards Bochefort. The 
rocks Sanadoire and Tuiliere (clinkstone) stand conspicuous on 
either side, and the Puy de Loueire on the extreme right. 



Plate IX. 

A View of the Valley of Chambon, one of the principal excava- 
tions which intersect the Mont Dore. It has its source in the centre 
of the group, and is directed in a straight line towards the east. 
The deep gorge called Chaudefour, which forms its upper extremity, 



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240 EXPLANATION OF THE PLATES. Affd 

probably one of the last central craters of the volcano, is bom i 
by perpendicular and degraded cliffs of trachyte, offering Hire? 
four varieties, superposed to one another in irregular beds wi 
intervening layers of tufa, the whole penetrated hy dyk** 
trachytic rock. At no great distance from the central bekri 
thick beds of basalt overlie first the trachyte, afterwards the ftm3 
mental granite, and, spreading far and wide into extensive platoac 
descend towards the main valley of the Allier with a gradual sLp 
which is, however, broken on some points by subsequent excm 
tions, on others, to all appearance, by partial elevations, oecasi*s 1 
perhaps by some of the convulsive throes of the volcano. Tben 
sheets of basalt are accompanied throughout their whole eitec 
by irregular deposits of volcanic conglomerate, varying from j 
coarse basaltic breccia to a fine pumiceous tufa. The eonjrf - 
merates generally support or alternate with the basalt, particukrh 
towards the lower part of the valley, where the granite is entire] v 
concealed by the accumulated volcanic products. The chief in 
terest of this view lies in the recent volcanic vent of Tartan r 
which has exploded in the middle of the valley, and by the quantin 
of matter it ejected dammed up the river so as to form the Lakt 
of Chambon, which is easily seen to have extended originally vj 
to the entrance of the Vallee de Chaudefour, but which has been 
lowered by the wearing away of its canal of discharge. Immedi- 
ately to the left of the cone of Tartaret may be perceived the 
commencement of its lava-stream, which continues to occupy the 
former bed of the river for a distance of thirteen miles. Further to 
the left rises the ruined Chateau de Murol, once a very strong 
fortress belonging to the family of d'Estaing. 



Plate X. 

Montagne de Bonnevie, a colossal cluster of columnar basalt, 
above the town of Murat (Cantal). A detached segment from the 
roi>eated currents of basalt which have flowed from the central 
heights, and are seen behind in cliff ranges. 



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I 



ft r| <t. Vi/A-olltc • urn's nil the nUiJt 1 wllk'li lllfitltti lh.- «.ih ■'„ 



b. Con* At EhMAK 
c v.iir-i ofplatrianl 




a, nuchr cCDnksiociej, 

& Frelweller (Hlnkitow 

<i. Hoot fa Done tttt»ti <m Mjri-. 

e. !>.**■ mil ('CHnltBtvni 



h l#roii* (Clinkstone 

» II. .iw ol M. Bertmtwl l« 

fc. rtuirvaux- nkiW •), 



J Yji ■!■ I 
Lli'l 

n 




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XPLANATION OF THE PLATES. 



241 



Plate XI. 





ch of the Basin of Le Puy and the Mont Mezen, 

jnt d'Ours near that town (Haute Loire). 

this point is exceedingly instructive, embracing 

^ features of an interesting and singular country. 

is a double volcanic cone of recent formation, 

- -" ' .ters have disappeared. The eruptions by which it 

^ -c^r^bnrst through a vast bed of volcanic breccia and 

still visible at the village of Ours, and forms a 

ky terraces from thence towards Le Puy. It rises 

limit of the freshwater formation, the remains of 

on every side, resting against the primitive margin 

which it was deposited. To the south-east are seen 

mm its of the Mezen ; and from thence to the north 

bounded by a chain of rocky eminences, the ruins of 

B current of clinkstone, which that volcano has poured 

rds the north. (See p. 157.) The last of these rocks, 

me, and another not seen in the drawing, near the town 

m Regnier, rise fiom a base of granite on the further side 

ire ; the current appearing to have occupied the foimer 

(Th-uLHrinlk^ river to some distance, and to have forced it to excavate 

R^iwimi/rertone through the whole mass of phonolite. The basaltic 

K<n < Q £ t j ie Mezex^ which, accompanied by prodigious eluvial 

' r ittions of brecciform conglomerate, overwhelmed the whole 

'of the freshwater formation, are obseivable in all directions ; 

& evident, from their being found on both sides of the Loire, 

is river's actual bed was not yet formed at the ®ra of their 

<t. The channel by which the Loire now issues from the basin 

Puy may be observed to have been pierced entirely through 

le, although at the very edge of the calcareous formation ; — a 

,ble fact, seeming to Bhow that even the softest marls under 

Electing cover of basalt resist meteoric erosion far more effectu- 

than granite itself. 

v ■ t was by the excavation of this narrow, deep, and tortuous gorge, 

the waters dammed back in the basin of Le Puy could only be 

R 




f 



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242 EXPLANATION OF THE PLATES. 

discharged. As the channel gradually deepened, the valley* 2 
now intersect its tertiary and volcanic formations were 
formed. That this was effected by degrees, and not by- 
debacle, is proved, 1st, By the undisturbed state of the 
scoriae. 2ndly, By the great variety of levels at which the 
lava-beds occur: they appear, in fact, as in the valley of 3 
Limagne, to be the more recent the lower the level they oocr-| 
thus marking the successive steps of the process of excavatii 
(See p. 180.) It is, however, possible that some cleft htcki 
through the granitic barrier by subterranean expansion may fc*H 
assisted the discharge of the lake in that particular direction. 

The prospect to the west is equally interesting. The horiran 1 
that side is limited by the vast chain of volcanic cones, which, cn\ 
mencing at the foot of the primitive heights of La Chaise-Diet 
reaches uninterruptedly to Pradelles, The lava-streams prodm 
by these eruptions have deluged an extensive and nearly level pfasi 
stretching from the foot of the range to Le Puy. This is intersect* 
by the channels of various torrents, and may be seen to consist - 
repeated currents of basalt, resting on the freshwater limestone. .' 
few insulated cones are scattered over the plain, and some occur * 
a considerable distance from the line upon which the greater numte 
of eruptions have broke forth. That near the village of Chaspinh* . 
on the slope of a massive granitic embranchment rising from nV 
river Siimene, is remarkable for its elevated position. It has appr 
rently furnished the lava-current of the Plateau de Fay, whick 
however, is now separated from it by the deep gorge by which tk 
Sumene joins the Loire. The large cone of Bar, near Alegre, whki 
still presents a very perfect crater, and those of St. Geneys and 
Couran, are conspicuous in the distance ; as well as those in uV 
opposite direction which rise from the Forest of Breysse, near 
Prezailles, on the western slope of the Mezen. 

The valley of the river Borne, from which rises the town of Lf 
Puy, the capital of the department of the Haute Loire, is not tfe# 
least interesting part of the view. Its numerous feeders, which 
unite near the remarkable insulated and regularly columnar rock 
called ** The Organ of Expailly," have each their channel cut 
through a system of basaltic beds, generally column i form, often 



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Appendix. EXPLANATION OP THE PLATES. 243 

? t. double, with a bed of conglomerate or alluvial matter interposed, 
pre and resting on the freshwater limestone strata. The great mass of 
ri volcanic breccia called the Rocher Corneille is seen rising above 
*1- Lie Puy, as well as the spiry pinnacle of St. Michel, formed of the 
;: same substance, and standing up in the middle of the town. A 
[ similar mass rises from the town of Polignao, as seen above, at a 
distance of about four miles. These rocks were favourable sites, 
i of course, for chateaux-forts in the good old times of rapine and 
r butchery ; and most of the towns of the central provinces of France 
were built under the protection of some such fortress. 

There are perhaps few spots on the globe which offer a more 
extraordinary prospect than this. To the eye of a geologist it is 
superlatively interesting, exhibiting in one view a vast theatre of 
volcanic formation, containing igneous products of various nature, 
belonging to different epochs, and exhibited under a great diversity 
of aspect. 



Plate XII. 



View of the Extremities of the south-western lateral Embranch- 
ments from the Basaltic Platform of the Coiron, as seen from the 
neighbourhood of St. Jean le Noir, on the road from Villeneuve de 
Berg to Viviers (Ard&che). 



Plate XTU. 



Volcanic Cone and Current of Jaujac (Ard&che). The cone rises 
from the middle of a trough-shaped valley, occupied by a coal- 
formation, and bounded on either side by ranges of granite and 
gneiss. A lava-current may be seen to proceed from a breach in 
the circuit of die crater, and descend into the valley of the Alignon, 
which it once filled to a considerable depth and width. The ex- 
cavation since effected by the river has exposed a mural range of 
columnar basalt about 100 feet high, and extending uninterruptedly 
into the farther valley of the Ardeche, and even some distance down 

R2 



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*»/ •.*-,. ,m»** v, *&** *-*-r *m*t Lftfv T!it* Tta^Sirai tr^Luc '!*<*« -re=. 

*+?*.*? '/,- r .v&sm t+xrx.% -.& xr«L.rA- A rraed GMRjit fGusiSt -:m*^ 
p^v,,*.? '„£ v,> xcsjfa. *tA &ii* i£* yjtzziz*s#y*£ efcjt -: *£* 3*ar=r- 
r,*vA', ,** '/ fr.^* ?^?y >>t^It wt&. Tut raZey » encased ty ^.* 
£/*/„Vs trSTt+w* of *t^ \jtfi,TttL of tbe Hajts YiTaraiav. Tbtr 
**,.'-« %/*, t.Wi*>A *.*r. ritX I, -rear* of Sj*niaiL cbesmt. In tfce L- 
**/•*, r,*/* * *o»',*r.>; eftM of ii-ferior aize to that of Montptzax. k. 
whsh hx* wA j/fvlv^4 any laTanftream. 

1 1 /^^> h<s rvti&rkwl il&t t\& rs&t amount of excaTation wtick b*r 
f^k' ri j/J^/^^ Jn thi* vulby %\jv*z the epoch at which h was filled .: 
io lUt' U,wl of tli^j Can tie of Pourchirol with liquid basalt, and tL* 
r#/Ht only throfi^li the \x*»ts%\t Imt to a depth of more than 100 ftr: 
through the tiri'lerlyin^ granite Cwhich w of a Tery hard compact 
hrtfMr*i; f r/i« only have been effected by the eroeiTe force of t ; - 
fttuenl* t/utt Jl/nti tlttm at jtmntt ; hince any more general and violent 
himIi of wabTii, of I he nature of a deltige or debacle, would not have 
h-fl HfMliMhirlmd tho two cones of loose scoriae, of which parts are 
wen In our ftketeh, and of which the materials are so incoherent that 
the foot Mink* atikl<<-do<*p into them. 



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Appkni>ix. EXPLANATION OF THE PLATES. 245 



Plate XV. 

La Coupe d'Ayzac, a volcanic cone with a very perfect crater, 
near Antraigues (Ardeche). The crater being on the opposite side 
of the hill is not seen in the drawing. 

A lava-current descending from it has been cut through by the 
river Volant. Its section forms a vertical rock, exhibiting three 
apparently distinct ranges of columns. Those of the lower story are 
very regular. The basalt rests on either side against the granitic 
cheeks of the valley whose bottom it occupied. This drawing was 
taken from the outskirts of the village of Antraigues, and from the 
foot of a remarkably isolated rock of columnar basalt, lying precisely 
at the same level with those seen on the opposite side of the river, 
with which it was certainly once continuously united. Similar but 
larger patches of the same current of basalt are visible on many 
points down the valley of the Volant for a distance of four or five 
miles, particularly in its concave angles. The excavation to which 
their insulated position is owing suggests the same reflection as that 
seen in the preceding engraving of the valley of Montpezat. (See 
p. 192.) By comparing this drawing with that given by Faujas of 
the same cone, it will be seen that in his directions to his draughts- 
man he must have trusted to memory, and that a very bad one. 
Besides the complete dissimilarity of form, it is absolutely impossible 
to see the crater of La Coupe and the basaltic range of columns 
above the river, together, from any one spot. 



Plate XVI. 



Sections of the Primitive Platform of Central France from N.N.E. 
to S.S.W. and from east to west. 



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246 EXPLANATION OF THE PLATES. 



Plate XVH. 

Fig. 1. Composite Sections or Profiles of the principal Hills in 
immediate neighbourhood of Clermont, showing the various l^ g^ 
at which contiguous beds of basalt are now found in the bash 
the Limagne, tending to prove the gradual excavation of tk 
valley. (See p. 202.) 

Fig. 2. Section of the Mont Mezen and part of the Freshin* 
Formation of Le Puy (Haute Loire). This seotion is takes fc 
M. Bertrand Boux's excellent work on the Environs of Le Pr 
The map which also accompanies that volume will be found i«r 
serviceable to geologists who may wish to explore that interests: 
district themselves. 

N.B. In both these sections the vertical scale is of coarse greath 
magnified as compared with the horizontal. 



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( *47 ) 



INDEX. 



iETNA, 30, 39, 42, 43 n., 44, 134 n.; 
compared with Mont Dore, 115, 116 n, ; 
great extent of some of its lava-currents, 
117 n. ; luxuriant growth of its chesnut- 
trees, 190. 
Agde, 196. 

Aidat, lake of, 74, 92, 103. 
Aig^ieperse, 12. 

Aiguiller, Pay de 1', 126, 131, 137, 136. 
Aix, 196. 

Alagnou, the, 146, 150, 151. 
Alais (Gard), 3, 4. 
Alassac (Correxe), 3. 
Alegre, 155, 184. 
Alignon, the, 190, 191. 
AUier, 2, 4, 7, 15, 17, 20, 26, 40, 112, 
134, 135, 139, 146, 154, 155, 176, 177, 
184, 211; probable cause of the fall of its 
celebrated bridge, 154 n.; extreme vio- 
lence of iU floods, t'6. 
Alpes, Hautes, 1. 
Alps, the, 186, 212. 
America, aqueous phenomena of (he tra- 

chytic volcano* of, 122, 123 n. 
Amethysts of Le Vernets, 2. 
Andes, the, 134 n. 
Angle, Plateau and Puy de 1', 123, 131, 

132, 133. 
Antraigues, 245. 
Anxa, 140. 
Apcher, 140. 
Apennines, the, 186 n. 
Ardeche, 3, 4, 38, 39, 154, 155, 162, 166, 
175, 187, 188, 189, 191, 192, 194, 195. 
Aides (Pay de Dome), 3, 140. 
Arniat, 77. 
Artias, 186, 193. 
"Arkose," M. Brongpiart's application of 

the term, 8. 
Arverai, traditional site of the city of the, 

106 and n. f. 
Asia Minor, analogy between the volcanic 
rocks <£ and those of Central France, 
210n. 
Aubenai, 38, 155, 162, 176, 185, 192 ; 
description of the basaltic dyke in its 
vkanitjr, 195, 196. 
Aubepin, 169. 



BASALT. 

Aubieres, 108. 

Aubin (Aveyron), 4. 

Aubrac, Canton <f , volcanic region of the, 
152, 153. 

Auliere, 187. 

Aumdne, Cheire de 1', 55, 58, 61 . 

Aurillac, 24, 25, 132, 148, 200 ; auriferous 
origin of its name o£ 151 n. 

Autun (Sadne et Loire), 4. 

Auvergnat, 79. 

Auvergne, 1, 2, 7, 11, 26 n., 28, 31, 32, 
33, 34, 38, 43, 47, 58, 60, 72, 81, 96 n., 
100, 169, 176, 178 n„ 181, 198 ; number 
of ruined "chateaux-forts" on its peaks, 
and ultimate fate of their lawless pos- 
sessors, 102 n. 

Auvergne, la Tour d\ 139. 

Auvergne, Limagne d\ See Limagne. 

Auvergne and Forex, surface elevation at- 
tained in the regions of, 1; vestiges of 
deposits of freshwater lakes there, 2. 

Aveyron, 3, 4, 5, 152. 

Aymard, M., 27, 35 n., 178, 218; his 
arrangement of the fossils, &c, of the 
Haute Loire district, 229-231. 

Ayxac, la Coupe d', 18C, 193 ; beauty of its 
crater and basaltic columns, 193, 194 

Baladon, Puy de, 133. 

Banniere, Puy de la, 44, 78, 82, 83. 

Banson, Pay de, 87. 

Bar, Montagne de, 184 ; its height, 233. 

Baraque, La, 63. 

Barbier, Puy de, 133. 

Barba, le Roc, 127. 

Barme, Puy de, 88. 

Barmet, Puyde, 61. 

Bamere, Puy, 211 ; its composition and 
height, 233. 

Basalt of Chalucet, composition of the, 98 ; 
preservative agency of the disposition of 
basaltic prisms, 106 n. ; olivine not in- 
variably a characteristic of basalt, 130 
n. ; question of the alternate superposi- 
tion of trachyte and basalt, 131 n. ; 
favourable occasion for observing the 
igneous origin of basalt, 142 and n. ; 
interesting character of the basaltic 



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248 



INDEX. 



BASALT, 
prisms of the Montague de Bonnevie, 
150 ; composition and formation of ba- 
saltic dykes, 173-175. 

Basalt of the Haute Loire and Ardeche 
(Velay and Vivarais). See Aubenas, 
Ayzac, Burzet, Coiron, Jaujac, Mont 
Mezen, Montpezat, Souillols, Thueyts, 
Velay, Vivarais. 

Bassignac, 4. 

Baume, La, 191. 

Bauzon, forest of, 185. 

Baveno, 2. 

Beaune, Valley of, 89. 

Beaumy, Puy et Lac de, 79, 80, 82. 

Beauregard, 19. 

Beauzac, 157. 

Bedarrieuz (Herault), 4. 

Benoit, Puy, 112. 

Bert (Allier), 4. 

Berze, Puy de, 106 ; its site, 108 ; its alti- 
tude compared with that of adjacent 
puys, 109 ; this puy the probable source 
of the basaltic current of Gergovia, 204. 

Besace, Put de, 88. 

Besse, Valley of, 134, 143. 

Beudant, M., remarks on the views of, 
relative to the superposition of trachyte, 
131 and 132 notes, 147. 

Beurdouze, 144. 

Beziers, 196. 

Blaves, 178. 

Boen, 28. 

Boiseghoux, 100. 

Bone-beds of Mont Perrier, locality of 
the, 135. 

Bones. See Human Bones. 

Bonnevie, Montagne de, 150. 

Borne, the, 175, 177, 181, 183 n. 

Bort (Puy de Ddme), 4, 149. 

Bouchet, Lake du, 185. 

Bouillet, M., 29 n., 35 n., 87 n., 217. 

Bourboule, la, 23. 

Bourglastic, 4. 

Bouttieres, les, 167. 

Bozat, Plateau de, 132, 133. 

Brassac, 4. 

Bravard, M., 135, 217. 

Bieocia, human bones found in, 181, 182. 

Breblak, M., 48 n., 120 n., 122 ». 

Bridges, natural, formed by incrusting 
springs, 22 ; single-arch bridge over the 
Allier, 154 ». 

Brion, 144. 

Brioude, 7, 154,182, 211. 

Brives (Correze), 4. 

Broochi, M., 19 n,, 48 n., 120 n. 

Brongniart, M., 8, 11. 

Brousson, Puy de, 94. 

Brunelet, 173. 



Buch, M. von, 33, 48, 51, 96 n^ 180 «. 

Building-stone, quarries of, 78, 128. 

Burat, M., 35 n. 

Buron, Picde, 113. 

Burzet, volcano of, 186, 187, 192; fre- 
quency of olivine nodules in its basaltic 
bed, 188 ; illustration of contractile force 
afforded by these nodules, to. and «-; 
idea suggested to the natives by the hori- 
zontal sections of basaltic columns, 188, 
189; form and dimensions of the 
columns, 189. 

Butte de Montpenaier, 12. 

Cacadogne, 125, 126, 133. 

Caddis-fly. See Phryganea. 

Caesar. See Julius Caesar. 

Caissiere, La, 92. 

Calcareo-volcanic strata of the Limagne, 
components and characteristics of the, 
15-17. 

Calcareous peperino, examples of, where 
found, 18-21 ; analogy between those of 
the Limagne and of the Vincentin, 19 au ; 
beauty of that of Pont du Chateau, 20. 

Calcariferous springs of Auvergne, lo- 
calities of the, 21-23. 

Camaldoli, 78. 

Canary Isles. See Lancerote. 

Cane, Grotta del, 85, 193. 

Cantal, 3, 38,39, 48, 49, 114, 115, 124 
n., 127 »., 134 is 139, 140, 144, 155, 
156, 167, 172, 175, 198, 199, 200, 
209, 211 ; vestiges of deposits of 
freshwater lakes in the, 2; similarity 
of its freshwater formation to that of 
the Limagne, 24; its locality and dis- 
tinctive features, to. ; difficulty of ascer- 
taining its original limits, 25. 

Volcanic Region of the Casta l, 
its figure : point of difference between its 
lava-current and that of the Mont Dome, 
145 ; character of its valleys, 145, 146 ; 
bulk, extent, and character of its conglo- 
merates, 146 ; their origin due to com- 
bined aqueous and igneous action, 147 ; 
site of its central crater, 148 ; vast extent 
of its basaltic beds, 149 ; interesting coo- 
figuration of the basaltic prisms of the 
Montagne de Bonnevie, 150; difficulty 
in removing them unbroken, to. ; alleged 
former auriferousness of the Jourdanne 
river-sand, 151 n.; relative age of the 
Mont Dore and Cantal volcanic remains, 
not determinable, 152 ; cause of impedi- 
ment to the basaltic ramifications E. and 
S.E. of the latter region, 154 ; height of 
the Plomb do Cantal, 232. 

Capucin, le, 131. 



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INDEX. 



249 



Carladez. See Vic en Carladez. 
Caasini's map, 52. 
Catania, 65, 157 n. 
** Gausses " of the Cevennes, 4. 
Central France. See France, Central. 
Cer (or Cere), the, 25, 146, 148, 151, 152. 
Cevennes, elevation of the rocks in the 
region of the, 2 ; defensive advantages of 
the district to the Protestants persecuted 
by Louis XIV., 4, 5, 
Cezallier, Montagues de, 139. 
Chadrat, 10. 

Chaise Dieu, la, 26, 154, 157. 
Chalar (or Chalard), Puy de, 80, 81, 94. 
Chalons stir Saone, central position of, 1. 
Chalucet, 23, 49, 198 ; composition of its 

basalt, 98. 
Chamablanc, 132. 
Chamalieres, 26, 179. 
Chambeyrac, 178. 
Chambon, 114, 124, 133, 134, 135, 140, 

141. 
Champagne, 197. 
Champanelle. See St. Genest de Cham- 

panelle. 
Champedaze, 144. 
Champeix, 141. 
Chandefour, 124. 
Channat, Puy, 44, 87, 104, 112; no 

vestiges of its crater visible, why ? 83. 
Channonat, 108, 204. 
Chantouzet, 137. 
Chanturgue and Clermont, C6tes de, once 

evidently united though now two, 104. 
Charade, Puy de, 84, 98 ; reasons for assign- 
ing a recent origin to it, 99, 100. 
Charlanne, 132. 
Charmont, Puy de, 94. 
Chaspiuhac, 178, 179, 184. 
Chastel, 150. 
Chastriex, 134 n.; 139. 
Chateau-gay, points of similarity between 
the plateau of, and that of J times, 100, 
104. 
Chsteauroux, central position of, 1 ; its 

lithographic limestone, 13. 
Chateix, 98. 
Chitelguyon, 23. 

Chatrat, Puy de, 109 ; its height, 233. 
Chaude de Fay, 178. 
Chaudesaigues, 23. 
Chaumont, Puy de, 71, 76. 
Chauriat, 19. 
Chaovet, 144. 

"Cheires," rugged fields of lava, 43; 
etymology of the term, to. n. ; cause of 
their ruggedness, 92. See Aumone, 
Come, Pariou. 
Cheix, les, 86. 



Cbesnut- trees, volcanic soil most favour- 
able to the growth of, 190. 

Chidrac, 135. 

Chiliac, 184. 

Chimborazo, 69. 

Chopine, Puy, 46, 71 ; a perplexing enigma 
to the geologist, 72 ; the authors deduc- 
tions regarding it, 73-75 ; origin of its 
elevation, 75 ; its height, 232. 

Chuquet Geneto, 87; explanation of the 
term u Chuquet," to. n. 

Civita Vecchia, 120. 

Clermont, 20, 21, 22, 23, 31, 33, 34, 40, 
67,85,86,98, 132, 211. 

Clermont and Chanturgue, C6tes de, once 
evidently united, though now separated, 
104. 

Clermont Ferrand, 39. 

Clersat, 66. 

Cliergue, Le, 128, 132, 

Cliersou, Puy de, situation and peculiar 
shape of the, 66 ; its caves perforated by 
the Romans, to. ; M. Ramond's hypothesis 
relative to this puy, 67 ; its height, 232. 

Clinkstone of Mont Mezen. See Mor.t 
Mezen. 

Coal-measures, strata associated with the, 3 ; 
localities of the principal coalfields, 4. 

Coiron, volcanic region of the, 161, 162; 
fanciful appellation bestowed by the 
peasantry on its basaltic phenomena, 163, 
164 ; basaltic rock of Rocbemaure, 164 ; 
instructive features connected with the 
basaltic currents of this region, 165, 166. 

Col de Cabre, 149 ; its height, 232. 

Coliere, Puy de, not noticed by previous 
writers, 86 ; characteristics of its basaltic 
products, 86, 87. 

Combegrasse, Puy de, 94. 

C6me, Puy de, regularity of the conical 
form of, 55, 56 ; prodigious dimensions 
of its lava-current and phenomena con- 
nected therewith, 56-61; its height, 
232. See also 66 t 79, 89. 

Compains, Valley of, 143. 

"Cones of eruption," 41 n. f. 

Conglomerates of Mont Dore, see Mont 
Dore ; tendency of conglomerates to waste 
into pyramidal form, 172 n. 

Coquille, Puy de la, 77. 

Coran, Chox de, dimensions of the crater, 
and composition of the strata of the, 111. 

Coran, Puy de, 13; circumstances which 
entitle it to attention, 111, 112. 

Cordier, M., 35, 232. 

Cordilleras, the, 134 n. • 

Corndlle, Rocher, 172, 175, 181. 

Cornon, Puy de, once the bed of the AUier, 
112. 



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260 



INDEX. 



CORR&ZE. 

Correze, 3, 4. 

Cdtes, Les, near Clermont, 12, 64 ; their 
height, 233. 

Coteuge, 144. 

Cour, Vallee de la, 126, 132. 

Cour-cour and Montagne de Cour-cour, 18, 
19. 

Couroo, 184. 

Craters, intenability of the theory of " ele- 
vation craters," 84 n. ; remarks on the 
alternating conditions of craters, 127 n. 

Crest. See Le Crest. 

Creux Morel, le, and its singular crater, 
70, 71. 

Crenze (Heranlt), 4. 

Crimea, the, 122. 

Croix de la Paille, 181, 182. 

Croix des Bouttieres, 156, 167. 

Croix Morand Plateau, 232. 

Croixet, M., 26 n.,' 135. 

Cros de Pexe, 137. 

Crouel, Put de, 18, 21 ; its height, 233. 

Croustaix, Montagne de, 180. 

Crouze, the, 23. 

Crystals of certain localities of Central 
France, beauty and variety of the, 2, 
20, 21. 

Cuzau, le Roc de, 126, 128, 133. 

Pallet, Puy de, 12, 15, 17, 112, 200; its 
height, 233. 

Daubeny, Dr., 35, 37. 

D'Aubuisson, M., 34, 51, 65, 72, 122 n. 

Davayat, 12. 

Decize (Nievre), 4, 211. 

Denise, Montagne de, 180, 181, 182, 183. 

Dent du Marais, 135. 

Desmarest, M., 31, 32, 33, 47, 52 n. 

Dienne, 149. 

Diluvian theory, remarks on the intenabi- 
lity of the, 204, 207 n. 

Dogne, the, 1 16, 1 25. See Dore and Dogne. 

Dolomieu, M., references to the opinions of, 
32, 48. 

Dome, Mont*. See Puy*, chain of. 

D&me, Petit Puy de. See Puy, Petit. 

Dome, Puy de, elevation, &c., of the, 45 ; 
composed entirely of domite, 45-47 (see 
Domite) ; its measurement, &c, 52, 53, 
232 ; mode of its prod action not indicated 
by its structure, 54. See also pp. 3, 4, 39, 
41, 48, 49, 50, 51, 66, 68, 69, 78, 86, 
87, 89, 129, 155, 232. 

Domite, a variety of trachyte, why so called, 
45; its characteristics, 46; its extreme 
liability to decomposition and volcanic 
nature, 47 ; hypotheses of various natu- 
ralists on the subject, 47-49; odour 
given out by it when rubbed, 53 ; M. le 



F08BILS. 

Coq's hypothesis relative to the 
puys, 70 «. 

Dordogne, 4, 5, 114, 126, 127, 132, 1S4 *, 
135, 137, 139, 140, 146, 149. 

Dordogne, Lot, and Aveyron, character of Ike 
lias underlying the oolite in the depart- 
ments of, 5. 

Dore, Mont. See Mont Dore. 

Dore, the, 112, 116. 

Dore and Dogne rivers, point of mice «f 
the, 116, 124, 128. 

Douc, Montagne de, 168, 171, 174. 

Drachenfels, 130. 

Drome, 1. 

Durbise, la, 128. 

Durtol, 64, 104. 

Egaules, 67. 

Egravats, Ravin de, 131 n. 

Eiffel, 78, 81. 

Emblaves, 26, 178, 179. 

Enfer, Puy and Vallee de 1% 94, 126. 

Entraigues, 194. 

Enval, 89. 

Eraignes, Puy d', 143. 

Erieux, 162. 

Escobar, M., 116 n. 

Esooutay, 165. 

Espinasse, la Name d', 94. 

Etang de Fung, 59. 

Etang, I', 83. 

Eternity. See Time. 

Etna. See -Etna. 

Euganean Hills, 130. 

Expailly, 171, 181, 182 ». 

Eysenac, Montagne d*, 180. 

Falgoux, 147. 

Faujas.de St. Fond, M., 31, 32, 165, 187, 

192, 245. 
Fauna of Central France. See Organic 

remains. 
Fay, 179. 
Fay-le-Froid, 167. 
Ferrand, Puy, 124, 125, 133. 
Ferrara, M., 116 n. 
Filhou, Puy de, 61. 
Fontanat, 86. 
Fontaulier, the, 185, 187. 
Font de PArbre, 86. 
Fontfredde, 89, 90, 91. 
Fontuiore, 64. 
Forez, the, 1, 2, 7, 28, 210. See Anvergne 

and Foiez. 
Fortresses, ruined, on the peaks of the 

Auvergne, and ultimate fate of their 

occupants, 102 n. 
Fossils and organic remains of the Hants 

Loire, 229, 230. See Organic remain*. 



Jt 



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INDEX. 



251 



FOURNET. 

Fournet, M. 9 35 n. 

Fraisse, Puy de la, 66, 67, 70. 

France, Central, division line of, 1 ; geolo- 
gical features of the country on either 
aide of this line, 1-5 ; theory of the 
French geologists relative to the pro- 
duction of its volcanic rocks, 200 ; table 
of heights of the volcanic districts, 232. 

Freshwater lakes of the tertiary period, 
proofs of the former existence of, 2, 6 ; 
probable cause of their drainage, 6 ; their 
boundaries easily recognisable, t'6. ; lakes 
of La Caissiere and d'Aidat, 92 ; peculiar 
features and probable origin of Lakes 
Pavin and Mont Sineire, 143, 144 ; ques- 
tion of the original level of the lake- 
basins of Central France, 210-213. See 
Cantal, Haute Loire, Limagned' Auvergne, 
Menat, Montbrison. 

Gannat, 10, 12. 

Gard, 3, 4. 

Garges, 4. 

Geology of Central France in the regions 
of the Auvergne, Fores, Gevaudan, 
Vivarais, and the Valley of the Rhone, 

1, 2; freshwater deposits of the ter- 
tiary period, 2; crystallizations in the 
granite, to. ; metals and their localities, 

2, 3 ; purity of the kaolin of Limoges, 
3 ; absence of the Cambrian, Silurian, 
and Devonian series of strata, 3; coal- 
measures and their localities, 3, 4 ; extent 
of limestone strata of the lias and oolite 
group, 4; aspect of the "causses" in 
the region of the Cevennea, 4, 5; lesson 
taught by geology relative to the im- 
mensity of the world's epochs, 208, 209 
and n. ; Sir Charles Lyell's summary of 
the geological characteristics of Central 
France, 213, 214. See Organic remains, 
Volcanic formations, Volcanic remains, 
Volcanic rocks. 

Gerbier des Jones, 157. 

Gerbison, 179. 

Gergovia, 12, 15; volcanic constituents of 
the mountain of, 17, 18, 200, 203; geo- 
logical and antiquarian interest attaching 
to it, 106 and n. f ; difference between 
its basalt and that of La Serre, 204. See 
Girou. 

Gevaudan and Vivarais, surface elevation 
attained in the region of the, 1. 

Gimeaux, 23. 

Gironde, 1. 

Girou, Puy, 12 ; this puy and Puys de 
Jussat and Gergovia originally a single 
plateau, 106; character of the stratifi- 
cation of the region, 107; line of contact 



HAUTE LOIRE. 

between the basalt and the limestone 
well defined, 108 ; its altitude compared 
with that of adjacent puys, 109; its 
height, 233. 

Godivcl, La, 144. 

Goul, the, 146. 

Goules, Puy des, 67, 69, 70 ; its height, 233. 

Gour de Tasana. See Tazana. 

Gouette, Puy de la, 71, 72, 73, 75. 

Grange, Pan de la, 125. 

Grange, Puy de la, 132. 

Granite rocks of Central France, varying 
character of the, 2. 

Graveneire, Puy, 44, 83, 99n., 100; its 
puzzolana in much request, 84; non- 
existence of a crater, to. and n. ; cha- 
racter of its lava rock, 85 ; its gaseous 
springs, t'6. ; industrious cultivation of 
the district, 86 ; its height, 233. 

Gravouse, Puy de la, 91, 92. 

Gresinier, 64, 105. 

Griou, Puy, 148. 

Gromanaux, Puy de, 87. 

Gros, Puy, 136, 137 ; its height, 232. 

Grotta del Cane, French springs analogous 
to the, 85, 193. 

Guery, Lake, 137. 

Guettard, M., an early observer of the vol- 
canic phenomena of Central France, 30 ; 
small credit given to his memoir thereon, 
31. 

Guiolle, La, 39, 150. 

Hamilton, Sir W., on the lava-current of 
-fitna, 117 n, 

Hamilton and Strickland, Messrs., on the 
volcanos of Asia Minor, 210 n. 

Hautechaux, Puy de, 133. 

Haute Loire, freshwater formation of the 
basin of the, 25; extent and depth of the 
superimposed volcanic rocks, ib. ; limits 
of the original basin, outlets of the 
Loire, 26 ; constituents of the lower 
aeries of lacustrine beds, 26, 27 ; extent 
and variety of their organic remains, 27 ; 
possible cause of the drainage of the lake, 
•6. ; points of resemblance between the 
rocks of this district and the peperino of 
the Auvergne lake basin, 28; probable 
cause of the accumulation of the water 
into a lake, 179. 

Volcanic Region of the Haute 
Loire and Ardeche (ci-devant pro- 
vinces of the Velay and Vivarais), 
154; natural boundary of this district 
and the Cantal, 155; its calcareous 
formation entirely cased in granitic rock, 
198; region of Mont Mezen and its 
dependencies, tee Mont Mezen. Volcanic 



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INDEX. 



HAUTK8 ALPES. 

phenomena of the Coiron, see Coiron. 

Kegion of the Velay and Vivarais, see 

Velay. See also 200, 206, 210. 
Hautes Alpes, 1. 
Herault, 4. 

Herculaneum and Pompeia, 30. 
Human bones, discovery of, in the breccia 

of the Montagne de Denise, 181, 182; 

results of a scientific discussion of the 

subject, 183; inferences deducible from 

the discovery, t"6. 
Humboldt, 51, 122, n. 

Iceland, resemblance of the Mont Baula in, 
to the Put de Dome, 50 n. ; enormous 
extent of the lava-current of a volcano 
in, 117 n. ; bursting of trachytic domes 
and currents through basaltic beds in, 
201 n.J 

Incrusting springs, natural bridges formed 
or forming by, 22 ; localities of similar 
springs, 23 ; different character of their 
sources, t'6. 

Infau, Puy de V, 94. 

Ischia, 130. 

Isere, 1. 

Issarles, Lake d\ 185. 

Issingeaux, 173. 

Issoire, 2, 211. 

Italy, 30 n. ; extinct volcanos of, 119 n. + ; 
natural parallel to the Romau roads in, 
189. 

Jaligny, 12. 

Jaujac, la Coupe de, 186, 191, 193; 
notion countenanced by its coal forma- 
tions, 190; its chesnut-trees, gaseous 
spring, and beautiful basaltic range, t'6. 

Jones, le (ierbier dea, 157. 

Jourdanne, the, 25, 148, 149. 

Joyeuse (Ardeche), 4. 

Juehat, Mont, 12. 

Julius Caesar, site of an unsuccessful siege 
by the legions of, 106. 

Julliat, 91. 

Jume, Puy de, 68, 77 ; its height, 233. 

Jumes, 100. See Chiteaugay. 

Jussac, 25. 

Jussat, Puy de, 12, 106. See Girou. 

Kaolin, supply of, for the factories of 
Sevres and Paris, whence procured, 3. 

Lacoste, M., on the volcanos of Auvergne, 

34. 
Lacustrine formations. See Freshwater 

lakes. 
Laduegne, 165. 
Laizer, M. de, 35. 



LIMAONE. 

Lakes and lake basins. See Freshwater 
lakes. 

Lamoreno, Pay, 89. 

Lancerote (a Canary Isle), referenc e s to 
volcanic eruptions in, 95 *.•, 180 n, 

Langngne, 184. 

Languedoc, 186, 197. 

Lantegy, Puy de, 71. 

Lantriac, 173. 

Laqui, 77. 

Lardeyrolle, 159. 

La-roche-lambert, 169. 

Laschamp, Puy de, not volcanic in appear* 
ance when seen from a distance, 89; 
marked effects of fire observable on this 
hill, 90 ; its height, 232. 

Lavas, laws determining the propulsion o£ 
49-51 ; rock of prismatic lava near Pool 
Gibaud, 61 ; great extent of various Lara- 
currents, 117 notes-, typical character of 
the various lava, 130 n. 

Laveille, 135. 

Lavoulte (Ard&che), 4. 

Layssac (Aveyron), 4. 

Le Coq, M., 35, 70 n., 87 n. 

Le Crest, village of, 102, 104. 

Le Grand d'Aussy's « Voyage en Au- 
vergne,' 33. 

Leironne, Puy de, 71. 

Lempde, 4, 154. 

Le Puy. See Puy, Le. 

Le Vernets, 2. 

Limandre, Lake de, 185. 

Limaone d'Auvebgne, 2, 24, 25, 27, 38, 
39, 64, 82, 112, 134, 198, 200, 202, 205, 
210, 211, 212, 213; extent and charac- 
teristics of its lacustrine formation, 7, 8 ; 
principal divisions of the lacustrine series, 
the sandstones and conglomerates, and 
M. Brongniart's opinion thereon. 8 ; the 
author's deductions on the same subject, 
t'6. ; identity of the marls and sandstone 
with the secondary new red sandstone and 
mar] of England, 9 ; character of the 
green and white foliated marls, 9, 10 ; re- 
markable extent covered by the indmaa? 
of the Phryganea (or caddis-fly), 11, 12; 
localities where they are best developed, 
12 ; probable cause of their aggregation, 
t'6. ; components of the calcareous marls, 
13; M. PomeTs deductions relative 
thereto, 13, 14 ; coincidence of Sir Charles 
Lyell's opinion therewith, 14; calcareo- 
volcanic strata of the district, 15-17; 
calcareous peperino, 18-21; calcariferous 
and incrusting springs and their localities, 
21-23. 

Limaone and Monts Dome, volcanic 
region of the, its extent and elevation. 



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40 ; its components and external charac- 
teristics, 41, 42 ; aspect of the lava- 
fields, 43 ; epochs of the formation of the 
chain o(puy$ f see Puts, chain of. 

Lime, limestone, carbonate of lime, pro- 
ducing causes of, in the regions described 
in this work, 198, 199. 

Limoges, 3, 67. 

Lipari Isles, 48. 

Loire, the, 1, 2, 3, 4, 7, 25, 26, 27, 28, 
157, 167, 171, 175, 176, 177, 178. 179, 
207, 211. 

Loire, Upper. See Haute Loire. 

Lot, 3, 5, 146. 

Louchadiere, Puy de, 56, 58 ; its majestic 
proportions, 78 ; appellation suggested by 
its crater, 79 ; its height, 233. 

Loueire, Puy de, 136. 

Louis XIV., 5, 102 n. 

L'Oulette, 178. 

Lox&re, 3, 4, 154 n. ; height of Mont Lo- 
xere, 232. 

Lyell, Sir Charles, references to the 
writings of, 9, 12, 14, 15 »., 27, 35, 
96 n., 116 n., 122 n., 135 n., 199, 217, 
223, 225, 226 ; his summary of the 
geological characteristics of Central 
France, 213, 214. 

Lyonnais, 28. 

Lyons, 150. 

Macalouba, 122. 

Madeira, 116 n. 

Malesherbes, M., one of the earliest ob- 
servers of the volcanic phenomena of 
Central France, 30, 31. 

Man, coexistence of, in France, with races of 
extinct mammalia, 183. 

Manson, Puy de, 233. 

Manzat, 80. 

Marais, Dent do, 135. 

Marcilly, 28. 

Margeride, La, 149, 154, 184. 

Mari, Puy, 149 ; its height, 232. 

Marine deposits, none later than the Juras- 
sic system in the regions described in 
this work, 197. 

Marmant (or Marmont), Puy, 18, 20. 

Marone, tiip, 146. 

Mars, the, 146. 

Marsat, 83. 

Massiac (Cantal), 3. 

Mauriac, 4. 

Mayence, 14. 

Mayet d'Ecole, 12. 

Maxayes, 58. 

Mazayes, lake of, 59. 

Mercceur, Puy de, 90, 158, 173. 

Meerfeld, 81. 



MONT DORE. 

Menat, tripoli basin of, 28 ; result of exca- 
vations in its sedimentary beds, 29 ; 
origin of its tripoli, t'6. 

Meye, Puy de la, or Puy Noir, 90, 91, 103. 

Mezen, 38, 49, 125 n., 175, 177, 180, 194. 
See Mont Mezen. 

Mianne, 161 n. 

Miaune, 179. 

Millefleur, Puy de, 13. 

Modena, 122. 

Monges, the, 59. 

Monistrol, 184. 

Mont, Montague de, 180. 

Montaigu, 28. 

Montaudou (or Montaudoux), Puy de, 84, 
99 ; its composition, 99 n. 

Montbrison, 2 ; extent and character of its 
basin, 28 ; its calcareous formation, 198 ; 
original limits of its lake basin, 210. 

Montbrul, les Balmes de, an accidental ex- 
cavation, 165. 

Mont Chagny, 12. 

Montchal, Puy de, 92, 143. 

Montchar, Puy, 89 ; its height, 232. 

Montchie, Puy de, 42, 88. 

Mont Crousteix, 171. 

Mont Dore, 33, 34, 38, 47, 48, 49, 
50, 67, 70 n„ 78, 82, 89, 95, 110, 
146, 147, 148, 149, 152, 155, 156, 
160, 167, 199, 201, 209, 211. Re- 
gion of Mont Dore. I. General 
Outline: its figure, 114; its ancient 
appellation, to. n. ; points of similarity 
between it and other insulated volcanic 
mountains, 115; circumstances which 
would reduce .Etna to the condition of 
Mont Dore, 116 n ; relative positions of 
its basaltic and trachytic products, 116, 
117; their occasional approaches to 
similarity of appearance, 118; extent, 
condition, and character of its conglome- 
rates, 118-121; facts tending to prove 
the co-agency of water in the formation 
of these conglomerates, 121, 122; causes 
of deluges during volcanic eruptions, 

122 ; effects naturally producible there- 
by, 123, 124; large annual fall and 
long continuance of snow on Mont Dore, 

123 n. II. Its Structure: heights of 
Pic de Sancy and Puy Ferrand, and 
prospect therefrom, 124 ; nature of the 
rock composing the mountain platforms, 
125 ; sulphur and alum deposits beneath 
the Cascade of the Dore, t'6. ; rich pastur- 
ages of the high-lands, marked contrast 
between the valleys and the heights, 125 
n. ; les vallees de l'Knfer and de la 
Cour, and their stratification. 126 ; local- 
ity of the principal vent (central crater), 



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MONT DORE. 

whence issued the trachyte formations 
of the mont, 127 ; )e Cliergue and its 
beds of building-stone, 128; height, 
slope, directions, and succession of the bed 
watered by the Cascade du Mont Dore, 
128-131 ; composition of the Plateaux 
de Rigolet, Bosat, and Charlanne, and the 
Puy de la Grange, 132, 133; highest 
points and average thickness of the 
granitic substratum of Mont Dore, 134 
n. ; valleys of Chambon and Besse, and 
bone-beds of Mont Perrier, 134, 135; 
characteristics of the Northern Flank, 
135-139; Southern Flank — greater 
abundance of basalt, 139 ; indefiniteness 
of the limits and scantiness of vegetation 
of this district, 139, 140. III. Kecent 
Volcanic Eruptions : site and compo- 
sition of the Puy de Tartaret, 140, 141 ; 
decisive proofs here afforded of the igneous 
origin of basalt, 142 and n.; characteristics 
of the basalt of Tartaret, 143 ; peculiar 
character and probable origin of the 
Lakes Pavin and Mont Sineire, 143, 144. 

Mont Dore, Cascade of, 125, 129, 131 *. 

Mont Dore les Bains, 23, 118, 129. 

Montelimart, 30. 

Montenard, Puy de, 95, 140. 

Montgy, Puy de, 93 ; its height, 233. 

Monti Cimini, 48. 

Montilhe, Roc de la, 138. 

Montillet, Puy de, 93. 

Monti Rossi, 65. 

Montjoly, 84 ; its gaseous springs, 85. 

Mont Jughat, Puy de, 12, 94. 

Montlosier, M. de, 35, 37, 48, 89; his 
agricultural labours, cause of his burial 
in unconsecrated ground, 238. 

Mont Mezen and its dependencies, cha- 
racteristics of the volcanic region of, 155 ; 
causes of the diversity of aspect between 
this and other regions, 155, 156; pre- 
dominance of clinkstone in its composition, 
156; extent covered by the clinkstone, 
157; strata on which the clinkstone 
rests, 158, 159 ; nature and varieties of 
the clinkstone, 160, 161; debateable 
origin of the clinkstone hills, 161 n. ; 
extent and flow of the basaltic currents 
of the district, 167 ; opinion of the author 
relative to their origin, to. ; facts whereon 
such opinion is based, 167-172; basaltic 
dykes and their formation, 173-175; its 
height, 232. See also 199, 209. 

Monton, Puy de, 120, 123. 

Montpensier, Butte de, 13. 

Mont Perrier, 14, 135. 

Montpexat, 185, 189, 192. 

Montpezat, laGravenne de, 186 ; extent and 



depth of the crater of, 187 ; beauty of ife 

basaltic columnar ranges, ib, 
Montpkux, 27. 

Montredon, castle of, 102, 104, 181. 
Montrognon, probably a r e mna nt of av iu - 

rent of Gergovia, 108 ; its altitude eaa*~ 

pared with that of adjacent pan, Itife. 
Mont Serae, 178. 
Mont Sineire, 143. 
MONT8 D6mr, 201, 205, 210. See Pxra* 

chain of. 
Mossier, M., opinion of, on the f uimri ia n st «f 

the puys, 48. 
Moulins, 4, 7, 197, 211. 
Moxun, 112, 113. 
Mur de Barrez, 25. 
Murat, 25, 148, 149, 150, 151. 
Murat le Quayre, 134 n., 137. 
Murchison, Sir Roderick impey, 35. 
Murol, 142. 

Nadavlhat, 102. 

Naples, 78, 120 ; Phlegrra fields o£ 1 1«L 

Napoleon, 154 n. 

Nechers, 120, 135, 141. 

Neidermennig, 78. 

Neptunians and Vulcanists, source of the 

contest between the, 101 n. Seembo 14? 

and n. 
Neris.23. 

Neufort, Puy de, 87. 
Nevers, 197*. 
Neyrac, 193. 
Niaigles, 91. 
Nievre, 4. 
Nohanent, 64. 
Noir, Puy (or Puy de la Meye), 90, 91, 

103, 203. 
Nugere, Puy de la, 77, 80, 83, 118, 128, 

201 ; its quarries of building-stone, 78. 

Olby, 89. 

Olivine not an invariable characteristic o/ 
basalt, 130 n. ; beauty of the olivin* of 
Burzet, 188. 

Olloix, Puy d% 110. 

Opme, village of, 235. 

Orcines, 63 ; its height, 233. 

Organic remains of Central France: pre- 
liminary remarks, 217, 218; fauna of 
the lacustrine strata, 218-223; pliocw 
fauna of the volcanic era, 223, 224; 
locality to which this latter fauna is 
almost wholly confined, 225; fish of the 
Basin of Menat (qu. post pliocene ?), to. ; 
fauna of ancient alluvia (post pliocene), 
226, 227 ; periods to which the alluvial 
fauna is referred by M. Potnel, 22* ; 
M. Aymard's classification, 229, 230; 



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INDEX. 



255 



ORGUES. 

observations on M. Aymard's catalogue, 

230, 231. 
Orgues, the, 181. 
Ours, Mont d', characteristics of, 241. 

Paille, Croix de la, 181. 
" Palais du Roi," les, 164. 
Palisse, la, 12. 
Palma, 115, 116 n. 
Pandreaux, les, 173. 
Panet, 25. 

Pardines, 14, 120, 135. 
Parioa, Pay de, presumably the product of 
one of the last eruptions, 61 ; dimen- 
sions of its crater, 63; inteiesting cha- 
racter of its lava flow, 63, 64 ; extreme 
raggedness of its ** cheire," 65 ; accumu- 
lation of puzzolana probably due to its 
eruptions, 66; its height, 232. .See 
also 67, 68, 86, 105. 
Paris, 3, 150, 212. 
Pasredon, Puy de, 109. 
Passis, M., 35 ». 
Paulhaguet, 155, 176. 
Pauniat, Puy de, 79. 
" Paves de Geans," 188. 
Pavin, lake, 143; its height, 232. 
Pennant, extent of an Icelandic lava-current 

described by, 117 ». 
Peperino. See Calcareous peperino. 
Perignat, 108. 
Pessade, Puy de, 133. 
Petrifying springs. See Incrusting springs. 
Peylenc, Rocbers de, 169. 
Peze, le Cros de, 137. 
Pezenas, 196. 
Phlegraean fields of France, 157 ; of Naples, 

119. 
Phonolitic mountains, tendency of, to waste 

into detached corneal masses, 159. 
Phryganea (or caddis-fly), remarkable extent 
of territory covered by the indusite of 
the, 11, 12; localities where they are 
best developed, 12. 
Pierre Neyre, 178, 179. 
Pierre-sur-Haute (Forez), 232. 
Piquette, Puy de la, 20. 
Pissis, M., idea of, relative to the super- 
position of basaltic currents, 201 ; his 
opinion on the elevation of the fresh- 
water formation of the Limagne, 211. 
Planeze, la, 149. 

Plomb du Cantal, 148 ; its height, 232. 
Poix, Puy de la, 18,21. 
Polignac, Rocher de, 172, 175. 
Polrainhac, 25, 151. 
Polognat, 120, 138. 

Pomel, M., 13, 14, 27, 35 n, 135, 217; 
his fauna of the lacustrine strata of 



Central France, 218, 223 ; pliocene fauna 
of the volcanic a?ra, 22.'J-225 ; fauna of 
ancient alluvia, 226-228. 

Pont Barraud, 12, 

Pont de Baume, 192. 

Pont des Eaux, 89. 

Pont du Chateau, 15, 18,20,40, 112,200. 

Pont Gibaud, 3, 23, 59, 60, 79, 96 ; sketch 
of rock of prismatic lava near, 57. 

Ponza, 48. 

Poulet, Puy de, 133. 

Pourcharet, Puy de, 93. 

Pourseille, 187. 

Pradelle, 155, 176, 185. 

Prades (Ardeche), 4. 

Prevost, M M 35 n. 

Prezailles, 176. 

Privas, 162. 

Prudelle, Plateau de, 104; decomposed 
character of its scoria, 105 ; difference 
between the two species of basalt of 
which its current consists, 105, 106 ; its 
height, 233. 

Puy, Le, 20, 25, 26, 158, 166, 168, 171, 
172, 173, 178, 180, 181, 182, 183, 185, 
199, 207, 210. 

Puy, Petit, or Petit Puy de Dome, and its 
" Hen's Nest," 54, 55 ; its height, 232. 

Purs, Chain of, or Monts Dome, situa- 
tion of the, 39 ; epochs of their forma- 
tion, 44, 45; hypotheses of various 
naturalists relative to such formation, 
47-49 ; laws determining the propulsion 
of lavas, 49-51 ; Vou Buch's theory, its 
strong and weak points, 51 ; puys north 
of Puy de Ddme, 54-82; eastern line 
of puys, 82-86; puys facing Puy de 
Ddme, 86, 87; puys south of Puy de 
Dome, 87-95. 

"Pyramids of Botxen" (Tyrol), cause of 
the preservation of the, 173 n. 

Pyrenees, the, 186. 

Querilh, Cascade de la, 131. 
Queuille, La, 136. 

Rambon, la Fontaine de, 23, 198. 
Ramond, M., 7, 34, 35, 48, 51, 67, 99, 110, 

114,119,120, 142, 213,232. 
Rantieres, 144. 
Raulin, M., 28, 35 »., Ill, 152, 201 *., 

211, 212 n. 
Recupero's notice of a lava-current of iEtna, 

117 n. 
Rhone, the, 1, 3, 31, 164, 165, 166, 167, 

193. 
Richelieu, Cardinal, 102 n. 
Rigo'.et, Plateau de, 128, 131, 132. 
Riom, 12, 28. 



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267 



VIVARAI8. 



89, 96, 138 ; sketch of rock of prismatic 
lara on its banks, 57. 

Solas, Puy d> las (or Puy de la Gravouse), 
91, 92 ; its height, 232. See Vache, 
Puy de la. 

Souillols, la Gravenne de, 186 ; peculiarity 
of its twofold columnar range, 191 ; pro- 
bable cause of their difference of struc- 
ture, 191, 192 ; its gaseous spring, 193. 

Spallanxani, dimensions of lava-currents 
mentioned by, 117 n. 

Springs, calcariferous. See Calcariferous 
springs. 

Springs of carbonic gas at Mont Joly and 
Royal, 85; atJairjac, 190; at Souillols, 
193. 

Springs, incrusting. See Incrusting 
springs. 

Sueiet, Great and Little, 55, 66, 67, 332. 

Sumene, the, 170, 178, 179. 

Suit le Comtal, 28. 

Switzerland, 32, 212. 

Tache, Puy de la, 133. 

Tallande, 92. 

Tarare, 3, 28. 

Tartaret, Puy de, 140, 141, 142, 143. 

Taupe, Puy de la, 94. 

Tazana, le Gour de, peculiarity of its crater, 
81 ; its probable origin, 82. See also 
143, 185. 

Teneriffe, Peak of, 38, 115; condition of 
its flanks, 116 n. ; bursting of trachytic 
domes and currents in, 201 n. $. 

Ternant, 66. 

Theix, Valley of, 90. 

Thiezac, 152. 

Thiolet, 79, 80. 

Thueyts, volcano of, 186; its character, 
189 ; its majestic colonnade of basalt, t'6. 

Time considered in reference to geological 
epochs, 208, 209 ; ideas suggested by the 
terms eternal, eternity, for ever, 209 n. 

Toulon, 196. 

Touraine, 14, 197. 

Trachytes of Mont Dore and Cantal, 49, 
50; trachytic domes of Iceland and 
Hungary, 50 n. ; trachytic volcanos of 
America, 122 ; possibility of establishing 
a distinguishing feature between basalt 
and trachyte, 130 n. ; question of the 
alternate superposition of the two, 131 
a. See Domite, Mont Dore. 

Travertin, natural bridge of, at Clermont, 
22. 

Tripoli basin of Menat, 28 ; probable origin 
of the tripoli, 29. 

Tuilfcre, La, 136, 137. 

Tyrol. See Pyramids of Botzen. 



I United States, kaolin exported from France 
I to the, 3. 
I Usclades, 185. 

Vache, Puy de la, and Puy de las Solas, 
created by showers of scoria? previ- 
ous to any emission of lava, 91 ; pecu- 
! liar condition of the clay in contact with 
the basalt, 92 and n. f ; scoriae of Puy 
I de la Vache, 93. 
! Vals, 194. 

Vandeix, Valley of,, 132. 

Vauquelin's experiments on domite, 53. 

Vayre, 20. 

Vegetable remains. See Organic remains. 

Velay, 2, 32, 34, 38, 60, 100, 155, 166; 
vestiges of deposits of freshwater lakes in 
the, 2 ; chain of recent volcanos in the 
Velay and Vivarais (Haute Loire and 
Ardiche), 175 ; extreme numerousness of 
the scoriae cones, 176; effects produced 
by the lava-currents upon the course of 
the Loire, 177, 178; M. Aymard's view 
relative to the subject, 178 n. ; pheno- 
mena connected with gorge of the Sumene, 
178, 179; parallelism of the volcanic 
eruptions of Auvergne and the Velay to 
those of Lanoerote, 180 n.; the Montague 
de Denise and the deposits of human 
bones in its breccia, 181, 182; results 
of a scientific discussion of the subject, 
183; moral ranges of columnar basalt at 
St. llpize, &c, 184; sites of lakes on this 
range, 185. 

Velay, Puy en, 154. 

Vernets, Le, 2. 

Verthaison, 18, 19. 

Vesuvius, 30, 31, 44, 127, 134 ». 

Vic en Carladez, 23, 25, 151. 

Vicentin, 19 n. 

Vichatel, Puy de, 92, 93. 

Vichy, 23. 

Vieille Brioude, 154 n„ 184. 

Villar, 63, 64, 104, 105. 

Villefort (Ardeche), 3. 

Villefranche (Allier), 4. 

Villejacques, 139. 

Villeneuve, 163. 

Villeneuve de Berg, 164. 

Viol, Puy de la, 87. 

Violan, Puy (Cantal), 232. 

Vivarais, 1, 31, 32, 34, 38, 39, 58, 100, 
155, 163 n., 178 n., 184. 

Vivarais, Bas, 166, 178; interest attaching 
to its recent volcanic remains, 186; 
magnificence of its slopes and valleys, ib. 
and n. ; its six volcanic cones, aee Ayzac, 
Burzet, Jaujac, Montpexat, Souillols, 
Thueyts ; probable point of union of its 
8 



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193; 

operating en the 
tasaltie and gr a nitic beds of taw m nlim, 
192. 193 ; presumed canae ef the presvr- 
•r" the Tofcaeic iiwsbii of this 
, 194; cherar4erh*iBeftheaaaakk 
dyke near Ube—, IS^ISS; presto de- 
daoUe from the km of this region, 205. 

Vhnrass Hurt, 2*>, 157. 162, 1*6, Ida, 
193. 

Vrriers,243. 

Volant, the* 193, 194. 

Volcanic "ene ef eruatian," 
aod dmiiptki n ef a, 41 a. f. 

Volcanic fonaatams en the derated enaitic 
pmt&rm of Central FraaKe—theories of 
Dr. Danheny mm! M. Uoatlosaen 37 : the 
author's reasons for dissenting therefrom 
•ft.; groups into which the entire db- 
triet is eeogrenhicalry dhkibie, 38, 39; 
relennk formation of the Veky tad 
Vrrarais, see Haute Loire, Ceiroe. Mont 
Mezen, Veky. 

Vokaaic regions: I. See Limagae d'Ao- 
rergne, and Pop, chain of. II. See 
Mont Dove. III. See CaataJL IT. See 
Haute Loire. 

Volcanic renmins of the interior of France, 
30; ignorance regarding them prerious 
to 1750, A.; Researches of MM. 
Gnettard and Makaberbes, 30, 31 ; dis- 
couraging reception of M. Guettard's 
memoir on the subject, 31 ; bis Clermont 
opponent, A. ; remits of the labours of 
MM. Desmarest and St. Fond, 31, 32 ; 
accuracy of Desmarest's maps, points 
wherein both naturalists were in error, 
32; Dolomieu and his igneous theory, 
•o. ; character of Le Grand d'Auasy's 
•Voyage en Amrergne/ 33; M. de 
Montlosier the Brat to establish the true 
nature of these remains, ib.\ MM. de 



t TOfcET. 

Bndfs, Lacaate <s, and 

on the subject, 33. $4 ; M. eV An 

■ » >hnit and their renal** 34; uav 

•f Baran RamotwTs m ■iiihib an an 
ohsenratians, 34, 35 ; Later arrnen aa» 
on— Dr. Daabenj, MM. W Cn4.Jbe.at. 
and Sir C. Lyell aod Sir R. Miiiihnn 
35 and a. 

Volcanic rocks, no traces of, an the aaa? 
of the I imnpaa trnafcwaanr nana 
14 ; characteristics of taw fsama* 
rata of that district, 1*4 
attempts of French geologists teaman* 
periodic classification of the ▼aleaaaraaa) 
of Central France, 2U0; fiactanadsm* 
rations dVmonstratiTe of the hvtksasna) 
of snch a dansificattoa, fcul-207; ftn> 
mensity of the periods required sar 6 
production of the raiioui esnsote Uaaa> 
able in geological surveys, 808. 200 aaani 
probable periods of the anoat reaaaamn> 
of the volcanic prod acta of Central Faam 
209, 210; analogy between theme* 
the rokanic rocks of Asia Manor, Him 

Volcanic rocks, the product of earlier aV 
tions, elucidatory obserTatioaa an, 9a*nn 
See Bene; Charade, Chantnrguev Caiaan> 
gay, Coran, Cornon, Gergnria, <4am 
PrudeUe, Roalade (Puy de la), tat 
(Puy\ St. Geuest de ChanafameUe, aV 
(la, Plateau of). 

Volcano* of Central France, »»ir+ s fTe hanaV 
published of the. See Volcanic reaanaV 

Volric, 78, 79, 88, 118, 128. 

Vukanists and Neptunian*, source ef fe 
contest between, 101 a. Srn aha am 
and a. 

Weiss, Dr., 137. 

Werner, bis theory and his school, 143 a. 

Tolet, 151. 



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