TKANSACTIONS OF SECTION C. 715 



scarcely more than a third of a metre broad, the tufa was fouud to extend for a 

 breadth of not less than thirty metres. 



As shown by the section given above, we find below the vegetable mould a 

 thick stratum of hard tufa, which we will name the fir tufa, and which is all 

 through its thickness quite full of leaves, cones, bark, &c., of the Scotch fir {Pinus 

 silvestris). In this bed we also find (but more sparsely) the leaves oi Betula 

 verrucosa and B. odorata, Populus tremula, Salix caprea, Vaccinium yitis id<ea, 

 Mniuin punctatum, Hypnum falcatmn, &c. The common spruce (Picea Abies) 

 grows now plentifully through all the valley, but is quite wanting in the tufas, 

 from which we may conclude that the formation of tufa had ceased before the 

 immigration of the spruce into the Gudbrandsdal. 



Below the fir tufa there comes first a clay (5) and then the stratum (4). Both 

 these strata are of inconsiderable thickness. The stratum (4) is a crumbling, 

 calcareous sandy clay, in which are found small lumps of hard tufa. In these we 

 find still some pine leaves, but besides them, in great numbers, the beautiful leaves 

 of Dry as octupetala, and (more sparsely) some other arctic plants, as Sali.v reticulata 

 and S. arbuscula. I found also in this stratum leaves of what appears to be 

 Cotoneaster vulgaris, besides some other plants. In the lower beds (3-1) neither 

 Pinus, Dryas, Sali.v reticulata, nor S. arbuscula is found. We learn from this 

 that Dryas and the other arctic plants named flourished at the place when Pinm 

 silvestris first immigrated. 



The bed (3) is hard and of considerable thickness. Its flora is quite diff'erent 

 from that of the strata already described. I name this bed the birch tufa. It has 

 no trace of Piiius, but is quite full of the leaves of different foliferous trees and 

 shrubs, as birch (only the mountain birch, Betula odorata), Populus tremula, Saiix 

 caprea, S. glauca, Mbes rubrum, &c. Betula and Populus occur to the bottom, 

 where also Hypnum falcatmn and Equisetum vanegatum are found. There is no 

 arctic flora at the bottom. The clay (2), which rests on the bottom moraine of 

 the old glacier, has no fossils. 



In this manner we find at Leine mainly two different beds of tufa. The oldest 

 of the two is the birch tufa, the youngest the fir tufa. Between them there is 

 intercalated a clay and a thin layer of tufa with Pinus, Cotoneaster, Dryas, and 

 other arctic plants. 



At the other and southern end of the long valley of Gudbrandsdal, not far 

 from where the river falls into the lake Mjosen, there is another deposit of tufa. 

 This deposit occurs at the farm Nedre Dal, in the district of Faaberg, 225 metres 

 above the sea-level. We find here the same two stages as at Leine, viz., birch 

 tufa and fir tufa, but the intermediate Dryas tufa is wanting. In the two beds, 

 which here also occur as separate blocks, we find mainly the same fossils as at 

 Leine. In the birch tufa at Nedre Dal occur Betula (only B. odorata), Popvlus 

 tremula, Prunus Padus, Salix caprea, S. nigricans, Myrtillus uliginosa, Equisetum 

 hiemale, &c., and in the fir tufa Pinus silvestris, Betula odorata, Vaccinium vitis 

 id^a, Linnrea borealis, &c. At the locality where the tufa occurs, no tufa is 

 formed at the present time. The spruce {Picea Abies) and Acer platanoides grow 

 abundantly at the place, but both are wanting in the tufas. 



Not far from Nedre Dal, at the northern end of the great lake Mjosen, m the 

 district of Birid, I found this summer a third deposit of tufa with the two same 

 separate stages, viz., birch and fir tufa. 



From all this we learn that the flora of the Gudbrandsdal (as, indeed, the whole 

 Norwegian flora) immigrated during alternating rainy and dry periods. At first 

 we have a time when glaciers flowed down the valley. After the ice had retired 

 there was first a dry period, when the clay (2) was deposited. Then the ramfall 

 increased again, and the springs formed a bed of tufa with such plants only as still 

 grow in the sub-alpine birch region of our mountain valleys. Then the climate 

 became drier. Dryas and other arctic plants descended from the higher mountains 

 and flourished, together with Cotoneaster, at the upper limit of the immigrating 

 pine forests, and soon afterwards the formation of tufa ceased totally, and the 

 clay (5) was deposited. Once again the rainfall increased, and a new bed of tufa 

 was formed. Durmg this moist period all the valley was clothed in sombre woods 



