1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 1/3 



to that rock*. We have only, therefore, to suppose, when some of 

 those powerful changes occurred to which the Alps were subjected, 

 that the more copious transmission of such hot springs and gases, 

 operating on a grander scale and w4th much more intensit}^ produced 

 commensurate changes of the carbonates into sulphates of lime, even 

 throughout mountain masses, and also disseminated flakes of sulphur 

 at intervals (as we find them) in the gypsum of the Alps. The con- 

 version of ordinary limestone into the sulphate is usually accom- 

 panied in the Alps by other phsenomena w^hich forcibly bespeak 

 metamorphism. The limestones situated near deep cracks and fissures 

 (in some of which hot springs still exist, as at Moutiers) are fre- 

 quently in the condition of a cellular hard tufa, sometimes siliceous, 

 which is known in Savoy under the name of " Cargneule." No one 

 can view this rock and not believe that it is the result of an action in 

 which much heat and gas were evolved. 



Although I have introduced the subject of these metamorphisms 

 of limestone whilst speaking of the lias and lower oolite, I am by no 

 means prepared to say, that the same transformation in the Western 

 Alps has not also been applied to strata both of older and younger 

 date ; just as limestones of different age in the Eastern Alps have been 

 changed into dolomites. But however this may be, great masses of 

 gypsum are certainly of about the age I speak of, inasmuch as be- 

 lemnites and ammonites and other shells of the lias, including the 

 Gryphcea gigantea, have been found in the associated strata at Bex 

 by M. Lardi. Wherever certain ammonites, such as the A. Walcotti, 

 and belemnites, or the Gryphcea incurva, Plagiostoma gigantea, &c., 

 occur in the strata which occupy the lower zone of the alpine lime- 

 stone, no one will dispute that such is about the horizon of the lias, 

 whatever may be the mineralogical character or colour and structure 

 of the rocks. 



In some tracts saurians have recently been found in the limestones, 

 as near Admont in the Austrian Alps, and at Perledo near Laico in 

 the Milanese ; but the small and peculiar forms from the last-men- 

 tioned locality do not afford such sufficiently clear testimony con- 

 cerning the age of the deposit f. I am not aware that any fishes 

 of the liassic age have been detected in the Alps. M. Heckl of 



* M. Joseph Bonjean, in an elaborate analysis of the mineral waters of Aix 

 (Annales des Mines, vol. xvi. Third Series, p. 299), whilst treating of various 

 effects produced by their acidulous vapours or gases, says — " Quelle que soit la 

 nature des corps soumis a Taction de cette vapeur (gas acide sulfhydrique) , ils 

 sont tous ronges et detruits dans un espace de temps plus ou moins long. Cest 

 ainsi que les pierres ealcaires, dont se composent les murs, se convertissent assez 

 promptement en sulfate de chaux a leur surface," p. 342. The inteUigent physician 

 of the baths, M. Despine fils, showed me the effects of this process, and gave me 

 specimens in which limestone several inches thick had been so metamorphosed. 

 This phaenomenon of conversion of carbonate of lime into sulphate is also clearly 

 described by Professor Mousson of Zurich, in a very able memoir on the district 

 around Aix and Chambery. The subject of the occurrence of thermal waters along 

 lines of dislocation is still more fully developed by this author in his sketch of the 

 geology around Baden in Switzerland. 



f See Memoir by M. Giuliano Curioni, Giornale dell' Institute Lombard© delle 

 Seienze, torn. xvi. p. 170. 



VOL. V. PART I. O 



