162 REPORT — 1844. 



which is required to make alum. According to my analysis this alum slate 

 from Bornholm and from the church of Opsloe near Cliristiania, contains the 

 following constituent parts : — 



Bornholm. Opsloe. 



SiUca 59-86 65-44 



Alumina .... 15-89 14-87 



Lime 0-99 0-15 



Magnesia .... 1-68 1-34 



Potash with a small quan- 

 tity of soda . . . 3-72 



Soda . . . 



Sulphur 0-82 



Iron 0-50 



Carbon 8-65 Oxide of iron 



Water 6-90 



99-01 



Carbon 



89-92 



Oxygen . . ."| ,., Water ... 



AzoTe. . . ^EmS" Oxygen . . .Undetermined. 



Phosphoric acid J Azote .... 



Phosphoric acid--' 



In comparing these two analyses, the close resemblance to each other is 

 certainly very interesting, in showing that during this formation the same causes 

 have been acting at the same time all over those parts of Scandinavia where 

 this formation is now found. The only real difference consists in the quantity 

 of silica, of which about 6 per cent, more are found in the Opsloe slate than in 

 that of Bornholm : all the other constituent parts come as close to each other 

 as they do, even in simple crystallized minerals from different parts of the 

 world. Those slates which I have analysed did not contain any pyrites in 

 particles that are visible to the naked eye. But in all places where alum slate 

 occurs, there also occur peculiar beds, which contain a much greater quantity 

 of pyrites connected with fossils that have not yet been determined, but which 

 seem to belong to the vegetable kingdom and may belong to some species of 

 fucoidal plants. The slate of one of these beds of the island of Bornholm 

 from the same quarry where the other slate had been taken, contained the 

 following quantities of sulphur, iron and silica, the only substances that 

 were determined : — 



Sulphur 3-72 



Silica 53-88 



Oxide of iron 6-80 



In Bornholm and in Scania (the southernmost part of Sweden) this slate 

 contains a great number of impressions of a fucoidal plant, of which Liebmann, 

 at my request, has been so kind to give the following description : — 



Ceramites Hisingeri. Alga caespitosa filamentosa ramosissima. Fila e 

 basi communi (radice) radiantia ad setam equinam crassa, fastigiato-ramosa 

 dichotoma; substantia interna venis duabus (siphoniis) creberrime genuflexis 

 et invicem spiraliter tortis (in modum generum Polysiphonias, Callithamnii, 

 Griffithsiae, Ceramii) percursa. 



According to Prof. Keilhau, Prof Boek and M. Esmark, the same Ceramites 

 occursfrequentlyinthealuminous Silurian slate of southern Norway. Recently 

 M. Hisinger has figured an imperfect specimen of it from Berg in the pro- 

 vince of Ostergothland in Sweden ; thus this Fucus appears to be characteristic 



