124 Professor HofTniann on the Geology of Massa Carrara. 



neighbourhood of Geneva presents many such examples, and 

 the observations of De la Beche on the environs of Nice, are of 

 decisive importance on this subject. It is consequently very 

 probable, that the limestone of the Apuanian Alp, which imme- 

 diately follows the Macigno, is to be considered as a Jura lime- 

 stone ; and we must then, as Savi has recently done, refer the 

 lower layers to the Macigno formation, a view which the author 

 does not consider as the correct one. It is certainly very sur- 

 prizing to find rocks like those described, clay and mica slates, 

 talc-slate, and gneiss, which leave no doubt as to their being con- 

 temporaneous or intimately connected with fossiliferous lime- 

 stone of the newer secondary formations. The slates follow not 

 only directly in entirely uniform connection with those lime- 

 stones, but they penetrate them, alternate with them, and are so 

 intimately blended with their masses, that the author considers 

 them even undoubted members of the secondary series. To 

 which of the known members of the secondary class these slates 

 are to be referred, we do not yet possess sufficient facts to enable 

 us to determine. The chief difficulty seems to be particularly 

 in the completely altered condition of the limestones. The mar- 

 ble, whose occurrence seems so remarkably connected with its 

 intimate union with the slate is certainly a limestone altered 

 by Plutonic agency. This we could not doubt, even though 

 the numerous relations of its union with dolomite and vesicular 

 limestone, its transition from compact and still unaltered lime- 

 stone, its penetrating veins, &c. were not observable. If, how- 

 ever, these altering actions have been produced through the 

 medium of the interlacing of the slates with the limestone, the 

 conclusion that the slates must have undergone alteration and 

 change cannot be avoided 



The only distinct unaltered members of this slate formation, 

 seem to be the Macigno-WVQ sandstone and the slaty marl of 

 Stazzema, and perhaps also the clay-slate occurring in its vi- 

 cinity ; as to whether these rocks at one time belonged to the 

 series of the Jura or Keuper formation, the phenomena now un- 

 der consideration afford no explanation. Mica and talc slates 

 are decidedly products of a deeply penetrating altering action, 

 and their connection with the gneiss inclines the author to be- 

 lieve that the probably long uninterrupted action to which all 



