Geology of Scandinavia. 295 



of very fine granular hypersthene sienite which traverse the me- 

 talliferous deposit of Schlangenberg in Siberia, has already re- 

 marked, how difficult it is to recognise them. When their 

 characters become indistinct they are generally confounded with 

 trap-rocks. But it is at present alleged, and this very cir- 

 cumstance is a new example of it, that the trap series contains 

 rocks of a very varied composition, although it is always equally 

 indiscernible. 



It would be desirable, that those very fine granular hyper- 

 sthene-rocks should be cleared of the confusion in which they 

 are at present involved, and this might perhaps be accomplished, 

 by studying carefully the series of steps through which the hy- 

 persthene- sienite passes, as it becomes more fine granular. Good 

 suites of specimens illustrating these transitions would be very 

 useful. 



% Trap-Rocks. — What I have recommended in regard to the 

 hypersthene rocks, may be recommended, I believe, in a general 

 way, in regard to all the trap- rocks of Sweden. When Cronstedt 

 and Wallerius first began to call attention to these rocks, whose 

 name they derived from the Swedish word treppa^ signifying 

 a stair, thoy could only characterise them by simple external 

 appearances. It is certain, as I have just stated, that these 

 same appearances are exhibited by many rocks of a different 

 composition. In general, this composition is indiscernible ; but, 

 by carefully examining the trap-hills, some parts might, per- 

 haps, be found in which the concretions are larger, and from 

 which we might procure specimens capable of being submitted 

 to the test of microscopic analysis, so advantageously employed 

 in regard to volcanic rocks, by M. Fleurian de Bellevue, and 

 especially by M. Cordier. Since modern researches have taught 

 us to consider hornblende, augite, and even felspar, as only 

 groups of species, the mineralogical analysis of trap-rocks has 

 become absolutely necessary for the science. 



True basalts, perhaps, occur among the trap-rocks of Swe- 

 den. Different authors have pointed out their localities, as, at 

 Kinnekulle on the banks of the Wenern lake, and in the hills 

 in the vicinity of Svebesholm and Hor in Scania.* Are these 

 true basalts, resembling in all points those of Auvergne ? We 



• Carte gc^ognostique des parties moyennes et m^ridionales de la SuMe ; 

 par M. Hisinger. 



