Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/202

164 164 AJfUHS HELLAXD OX THE FJORDS, LAZES,

and present in many lands ; we next remark that where the line of perpetual snow lies high up, the cirques chiefly occur at higher levels : where the limit of snow descends, the cirques are also found at lower levels. According to Professor Gastalcli the Alpine cirques are found at heights between 2000 and 3000 metres ; around the Justedalsbraeen they are numerous at the level of 1200 metres ; on the Jotunfjelds at heights above 1600 metres. The bottoms of the cirques on Istinden Mountain, in rinmark, are 800 metres above the sea ; nay, in Kvalo Island, in the same district, according to Mr. Lorange. cirques lie only a few feet above sea-level. Comparing these heights with the snow-line, which is 2500 metres in the Alps, 898 to 1460 metres (according to Prof. Sexe i near the Justedals- braeen, 1600 metres (according to Prof. Keilhau) in the Jotunfjelds, and 900 metres in Seiland Island in Finmark, we see that cirques are chiefly found near the limit of perpetual snow, which is to be expected when we remember that this limit is most favourable for the formation of isolated glaciers. That the cirques also occur at lower levels than the snow-line is in harmony with the occurrence of glaciers, which, as is well known, are found much lower down than the limit of perpetual snow ; and the occurrence of a cirque in Kvalo only a few feet above the sea-level harmonizes with the other observations, when it is seen that these cirques are filled with glaciers.

In Greenland, alon:: the mainland round Disko Bay. where the mountains are low and the conditions unfavourable to small isolated glaciers. I saw no cirques ; but on arriving at the Waigat and the Umanak Fjords, where the mountains are higher and isolated glaciers verv numerous, cirques also are numerous : and as isolated glaciers are here capable of being formed and maintained at an inconsiderable height above the sea, the cirques also occur often at but slight elevations. The fact that the cirques are commonly situated on the north sides of the mountains or the south sides of the valleys, shows a dependence on the glaciers ; for the north sides of the mountains, where the snow is less exposed to the sun's rays and to warm south winds, are favourable to the formation of glaciers. As to the way in which the glaciers excavate the cirques. I may quote another observer. Lieutenant Lorange (Xorwegian Eoyal Engineers), who mapped the country round Justedalsbrseen. He, though not a pro- fessional geologist, independently formed the opinion that the cirques and some fjord-valleys of Xorway were formed by glaciers. "Cnder the glaciers in cirques, where a space intervened between the bed of the cirque and the ice, he saw a great many stones, some of which, sticking fast in the glacier, were quite lifted up from the bed of the cirque, while others were touching or resting on it ; he thinks it pro- bable that as the temperature around the glaciers constantly varies about the freezing-point, the incessant freezing and thawing of the water in the cracks in the rock may split it, and the glaciers may do the work of transportation for the fragments thus broken loose. On examining the interior of an empty cirque, we observe that a