Geology (rf Scandinavia. 297 



occurs there in veins, and, in particular, pretty often in the in- 

 terior of the crystals of labradorite, which the crystals of epi- 

 dote have evidently acted on, to allow of their own formation 

 and enlargement. Some geodes in this melaphyre contain bitu- 

 men. Krogskov ought to furnish an ample harvest. 



The escarpements of Hohnestrand shew a passage from me- 

 laphyre to basalt. Holmestrand ought to detain the person in- 

 trusted with making the collections for several days. 



The zircon-sienite occurs in its most characteristic forms in 

 the vicinity of Laurvig, and also in the direction of Stavem. 

 This beautiful rock here extends over entire square leagues ; 

 and it is therefore unnecessary to point out more particularly 

 proper places for collecting specimens of it. 



It again appears at Egersund, to the south of Bergen, where 

 its extent has not been examined, although this would be well 

 worth the trouble. Farther on towards the north it is not found. 



I shall not confine myself to merely recommending the ex- 

 pedition to search for all the varieties of rocks which I have 

 mentioned, and to make complete collections of them. The re- 

 markable circumstances of the mode of occurrence of these 

 rocks, the manner in which they often intersect the adjacent 

 rocks, or disturb or cover them ; the modifications of texture, 

 and sometimes even of composition, which the latter exhibit 

 near the point of contact, ought to be studied in detail and 

 illustrated by good sets of specimens ; they ought also to be 

 figured. 



Our two members, MM. Alexandre and Adolphe Brong- 

 niart, during thisir travels in Norway and Sweden in 1824, 

 observed, especially in the environs of Christiania, numerous 

 masses of eruptive rocks, such as, for instance, melaphyres in- 

 jected among pre-existing rocks. M. Adolphe Brongniart has 

 made drawings of the positions and the mutual penetrations of 

 these rocks, which are both picturesque and geological, and 

 which I would recommend to the imitation of the naturalists 

 and artists of the expedition. 



It is known how important, in a geological point of view, 

 those veins have become which were discovered by Hutton in 

 Glen Tilt, in Scotland, piercing through the superimposed 

 limestone. Norway abounds in phenomena of penetration no 



