160 AMTLND HELLAND ON THE FJORDS, LAKES,
392 metres. The mountain of Tronfjeld, in Osterdalen, consists of gabbro, in which are small quantities of serpentine ; the summit is 1744 metres above the sea, and 150 metres below this, on the western slope, a rounded block of granite was found. Boulders of laminated quartzite with rounded edges occurred up to a somewhat greater height, so that the upper limit of erratics is here about 1600 metres. The height of the bottom of the valley of Osterdalen is about 500 metres. Erratics of serpentine, laminated quartzite, and granite are found on Solen Mountain in Rendalen * : this mountain consists of red sand- stone, paragonite schist, and conglomerate, the height of its summit being 1788 metres. According to Mr. Tornebohm's measurement, boulders occur to within 47 metres of the summit, or up to 1741 metres above the sea. The height of the country below this mountain is about 700 metres. Suletind Mountain in Yalders is 1770 metres high ; according to Keilhau an erratic is found on its summit. The height of Utrovand Lake (985 metres) may be taken as the general height of the country at the foot of the mountain. In South-eastern Norway, where the mountains are much lower, boulders, of course, cannot be observed at heights like the above ; but on Graagalten Mountain, above Lake Soneren, I found erratics up to the summit, 756 metres above the sea, the elevation of the lake being 118 metres. On the mountain of Skrimfjeld, south of Kongsberg, erratics occur up to the summit and roches moutonnees near to it ; this is 900 metres, the height of the country below being about 250 metres.
Assuming, then, that no important changes in configuration have taken place since the transportation of the boulders, we have the approximate minimum thickness of the glaciers given in the following Table : —
Thickness of the Glaciers during the Glacial Epoch.
metres.
Height of the groovings in the isle of Varaldso 569
Depth of the Hardanger Fjord inside the isle 631
Thickness of the glacier in the Hardanger Fj ord 1 200
Height of erratic boulders in the Sulends 511
Depth of the Sogne Fjord inside the Sulends 1244
Thickness of the glacier in Sogne Fjord 1755
Height of groovings above Aurlands Fjord 606
Depth of this fjord 275
Thickness of the glacier in Aurlands Fjord 881
Height of groovings above Sor Fjord 471
Depth of this fjord 392
Thickness of the glacier in Sor Fjord 863
- Toraebohm, "Om flyssblock och terasser," Geol. Foreningens Forh. vol. i.
and Schlotz," Sparagmitkvarts-fjeldet," Nyt Mag. f. Naturw. vol. xx.
