of Serpentine, Sfc. in the Apennines. 171 



summit of the mountain, and in which the compact oxide 

 of manganese is worked, that apparently occurs in dissemi- 

 nated nodules. This jasper is most generally red, and con- 

 tains portions of agate ; it is traversed by numerous veins of 

 white quartz, which present cavities lined with crystallized 

 quartz. When the Col de Beverone is passed, the jasper is 

 seen on the left, towards the summits of the mountains, 

 always resting upon the limestone and marly schist, shewing 

 its existence by rolled fragments on parts of these mountains, 

 and at a distance by its occurrence on thick beds, and by 

 the reddish colour of these beds. The superposition of 

 these two rocks could not be discovered from this obscure 

 disposition ; but being known, the analogous positions are 

 easily traced here. Yet, as the serpentines do not rise to 

 this height, so many rocks are not found, and it is only in 

 descending from Beverone towards Madignano, that they 

 are again discovered in the same relative position. While 

 mounting towards the summit of Mont Silva, the jasper is on 

 the right or East, and the limestone and marly schist on the 

 left or West, rising from beneath the jasper ; and as this 

 calcareous formation occurs throughout a considerable ex- 

 tent, all its peculiarities may easily be studied. 



The mixture of marly schist and compact limestone is seen 

 to be still more frequent and complete here, than at the base 

 of the mountain. This portion of the calcareous rock mixed 

 with clay appearing to have collapsed more at the general 

 desiccation of its beds, than the pure compact limestone, 

 open clefts have resulted, which have been penetrated by 

 marly schist. The latter being removed by some cause 

 which it does not belong to my subject to search for, the 

 lower portions of the limestone beds have remained divided 

 into a multitude of prisms perpendicular to the plane of the 

 beds, and separated from each other by open clefts. This 

 disposition, remarked by Targioni and the Italian geologists, 

 has caused the name of alberese costellino to be given to it, 

 i. e. knifestone, because the ridges of the prisms are often 

 very sharp. If the calcareous rocks affording these prisms 

 were cut near their base, and perpendicular to their sides, 



