observable in the Secondarjj Stratified Rocks. 217 



of dolomite and augite porphyry, close to the lake, but not ex- 

 tending far inland. The map is one of considerable detail, and 

 shows other masses of dolomite in contact either with the au- 

 gite porphyry or the granite, which, if not changed limestone, 

 occur at least singularly among it. There will also be ob- 

 served a very great connection between the granite and por- 

 phyry, more particularly as regards their line of direction, that 

 of the great range of the Alps. The granite is of that kind 

 commoidy known as the granite of Baveno. 



Now be our opinion of M. Von Buch's theory of the forma- 

 tion of dolomite what it may, the fact of the passage of this 

 gray compact stratified limestone into an unstratified crystal- 

 line rock charged with magnesia, and the presence of a large 

 mass of augite porphyry on the side of the crystalline rock, 

 remains still the same. With the theory that has been con- 

 nected with these appearances, I have nothing now to do; my 

 present purpose is only to show that these compact gray lime- 

 stones and dolomite may both belong to the oolite formation. 



Fortunately the neighbouring lakes of Como and Lecco, 

 which I examined last May, are very instructive as regards the 

 connection of these limestones and dolomite. If we proceed 

 from Como by the lower lake of the same name to Bellaggio, 

 we meet only, if we except gravels and transported blocks*, 

 with gray compact and schistose limestones, on either side of 

 the lake, until we reach either the side of a mountain named 

 Croci Galle, or the opposite island of San Giovanni Battista. 

 But if we proceed from Lecco by the lake of Lecco also to 

 Bellaggio, the shores on both sides are formed of dolomite, if 

 we except some gray schistose and compact limestones with 

 anthracite at Olcio and Lierna, a few contorted beds of the 

 same rocks opposite Abbadia, and a mass of gypsum included 

 in the dolomite near Limonta. Now if the direction of the 

 beds be worth any thing, part at least of the gray limestones 

 of the Lago di Como are converted into dolomite in the Lago 

 di Lecco, as indeed is better observed by ascending the Monte 

 San Primo, situated between the two lakes, where looking 

 along the line of direction of the limestone beds constituting 

 its ci'cst towards the lake of Como, we have limestone; towards 

 the lake of Lecco, dolomite. Some of these limestones seem to 

 represent the lias, for at Moltrasio and other places we find 



• Tlicsc blocks arc in great abundance in tlic vicinity of tlie Lago di 

 Como i they occur at very great lieiglits above tlie level of the lake, fre- 

 quently of very considerable size ; tbey are composed of granite, gneiss, 

 mica slate, talcose slate, Ac. fic, and may be considtncd as the records of 

 tlie violuiit cuiastroiihe which has loin them fio)n the hiyh Aljjs and car- 

 ried them into their present position. 



N. S. Vol. G. No. ^:i. Sept. 1829. 2 F belem- 



