115 



M. Bou6 to know, that all the great tracts to the south of the Danube 

 anJ beyond the countries of Transylvania, which he had formerly 

 described, were untrodden by g; ologists. Residing, I believe, more 

 than two years in these rude provinces, he niad^^ hini-self master of 

 their stalistics and geography ; and, publishing a geological sketch of 

 Turkey in Europe, he has also furnished us with a geological map of 

 tiiat country*. Of jiala^ozolc rocks, as distinguished by their fossils, 

 Turkey affords few traces beyond the small tracts at Constantinople 

 occupied by true Silurian strata, whir^i Mr. Hamilton and Mr. Strick- 

 land made known to us. Great masses of the inferior rocks are 

 stated by M. Bone to be in such a metamorphic and crystalline state, 

 and to be so penetrated by a great variety of intrusive rocks, that it 

 is very difficult to determine their age. With some very doubtful 

 exceptions, no secondary rocks, in ^.hort, can be recognized as of 

 higher antiquity than the Cretaceous system, which having, for the 

 most part, the crystalline character which it puts on in all the Me- 

 diterranean countries, is still divisible into Lower and Upper de- 

 posits, the former consisting of schists and sandstones with fupoids, 

 which represent our greensands, and the latter of a white marble 

 with numuMilitic strata, the equivalent of our chalk. Overlying 

 these, our author mentions and lays down upon his rnap no less than 

 thirty tertiary basins, thus showing a great analogy to Asfa Minor. 

 For such marked results our special acknowledgements are due to M. 

 Boue, than whom no one has accumulated a greater number of facts 

 in many parts of Europe ; his numerous and difficult journeys ha- 

 ving been performed entirely at his own cost, and chiefly for the 

 |)ure love of geology. 



PiedmorUese Alps. — In the north of Italy and the Western Alps, 

 considerable advances have been made by the labours of M. Sis- 

 montla, who is engaged in the formation of a geological map of the 

 Piedmontese territory, which, with the map of Sardinia by the Cava- 

 lier Marmora, will give a complete view of the structure of the Sar- 

 dinian dominions. To accomplish this, M. Sismonda has been la- 

 bouring during the last ten years ; and I am led to believe that in 

 about two years his great map v.'ill be fini^hed. in the mean time, 

 and in addition to various memoirs with which you were previously 

 acquainted, he has recently published descriptions of the Piedmontese 

 Alps. Dividing the great mass of crystalline rocks, he shows that the 

 inferior portion may really be called primary gneiss and mica schist ; 

 although other rocks, which have to a great extent the same litholo- 

 gical characters, but which alternate with quartzose grits, and repose 

 unconformably upon the first series, are truly metamorphosed aqueous 

 deposits. Considering the great derangement and changes to which 

 these latter rocks have been subjected, the author does not, however, 

 attempt to fix their age. On this point I may be permitted to 

 observe, that Professor Sedgwick and myself have pointed out the 



* A geological map of a part of Servia and Albania, ])repared by Colonel 

 Lassie, from the observations of M. Visquenil, has, by the assistance of M. 

 Bou6, completed our acquaintance with the geology of this distant part of 

 Europe. 



