AITNIVERSAEY ADDRESS OP THE PRESIDENT. IxXV 



will be found a notice on the cupriferous deposits contained in 

 the Serpentines of Central Italy. It is well known that indica- 

 tions of copper, connected with the outbursts of ophiolitic rocks 

 in Italy, are very abundant, but many of them are so unfavourably 

 placed as not to admit of their being worked advantageously. The 

 mine of Monte Catini is the only instance of successful opera- 

 tions amidst the ophiolitic rocks of Central Italy. The author 

 commences by describing the eruptive rocks of this region, which 

 have already been subdivided by Prof. Savi into four classes, each 

 of which corresponds with a distinct period of formation. 



I. Old Serpentine, posterior to the Lower Eocene, but anterior 

 to the Upper Eocene. This is often traversed by dykes of Eu- 

 photide and Diorite. 



II. Euphotide or Granitone, contemporaneous with the depo- 

 sition of the Upper Eocene. 



III. Diorite, Afanite, and Ophite ; contemporaneous with and 

 subsequent to the ophiolitic Macigno. 



IV. Serpentine rocks of the second eruption, newest Serpen- 

 tine ; subsequent to the deposition of a part of the Miocene 

 formation. 



All these roclis vary much locally in their mineral characters. 

 Their chronological position is fixed by the dykes and veins which 

 they successively send forth into the preexisting rocks. 



The author then proceeds to describe the metamorphic rocks 

 which are found in close juxtaposition with the ophiolitic rocks 

 in Central Italy. He shows Jiow the preexisting sedimentary 

 rocks must have been more or less altered and metamorphosed in 

 proportion as they were exposed to the inflaence, both chemical 

 and mechanical, of one or more of the outbursts of the eruj)tive 

 rocks. He quotes Prof. Savi as having long ago demonstrated 

 the existence and origin of many metamorphic rocks in Tuscany ; 

 and also quotes his account of the Gahbro rosso, so cliaracteristic 

 and important a rock to the Tuscan miner, as containing the most 

 important cupriferous formations in that part of Italy. The posi- 

 tion of the metamorphic sedimentary rocks is generally very 

 remarkable, following the outlines of the eruptive rocks. This 

 he believes to be one reason why so many distinguished geologists 

 have looked upon the Gahbro rosso of the Serpentine mountains 

 as an eruptive rock, although Savi had long ago pointed out its 

 metamorphic origin. 



The metamorphic rocks are divided into two classes : 



I. Argillaceous rocks altered by ophiolitic outbursts. There is 

 great variety in the extent to which these are altered ; some have 

 only undergone a change of colour, and have preserved their stra- 

 tified structure. Others have undergone a complete modification 

 of structure as Avell as change of colour, and have acquired a 

 siliceous hardness ; their structure then becomes compact or 

 brecciated, or sphei'ical, besides undergoing many otlier changes, 

 having sometimes been almost fused or melted by contact with 

 the eruptive rock. It is to the third of these structural changes- 



