172 M. Brongniart on the Frcsh-iioater Foi-mation of Rome. 



daloid with a brown base, partly resembling that of Holme- 

 strand, has been found in isolated fragments near the Sund, 

 and it will probably be met with in place. There are green- 

 stone dykes in Scanm, and the country of Christiana in Nor- 

 way, in the latter country they traverse transition limestone 

 and clay slate ; in Scania, they occur in the slate, and also in 

 the sandstone and gneiss. Trap dykes are also seen in the 

 environs of Rostanga, Konga, and Andrarum. 



Alluvion Formations. — The base of all these in Sweden is 

 composed of the remains of primitive rocks; and it is seen, 

 fi-om the nature and disposition of the rolled pebbles, that the 

 cause which has given birth to these extensive formations 

 acted from north to south. The presence of stones on the 

 coast of Northern Germany, derived from Swedish rocks, yet 

 more clearly proves this fact. The great catastrophe which 

 has produced these immerous alluvions is the last which the 

 Scandinavian peninsula has experienced*. 



Bog iron -ore is met with in Smoland, Dalecarlia, and 

 Jemtland ; where it occurs in sufficient quantity to supply the 

 wants of the principal forges of those countries. 



10. On the Fresh-water Format ioji of the Environs of Rome; 

 hy M. Alex. Brongniart f. 



M. Omalius d'Halloy was the first geologist who referred 

 the calcareous rocks so well known at Rome and Sienna, un- 

 der the name of travertin, to the fresh-water formation ; and 

 who showed that, with the exception of fresh-water shells, 

 which he did not find in the travertines of Tivoli, this lime- 

 stone presents all the characters of minute structure, po- 

 sition, and mode of occurrence on the great scale, which be- 

 longs to the fresh-water formations, such as we have charac- 

 terized them. They more particularly j)resent those singular 

 tortuous canals so constant in the fresh-water limestones of all 

 countries, tubular cavities which had not escaped so excellent 

 an observer as M. Von Buch, who had described them with 

 perfect accui'acy before he knew their importance as a general 

 character of these formations. 



The extent of this fresh-water formation of Southern Italy, 

 its importance both as it relates to geology and the arts, au- 

 thorizes me in entering into some details respecting its Ibrma- 

 tion and position relatively to other rocks. 



* This formation appears evidently to be the same with the Diluvium of 

 British gcoiogists. — Trans. 



f Extracted from the Dcsc. Gcol. dcs Env. de Paris, by MM. Cuvier and 

 Brongniart. 



M. Omalius 



