Sir R. R. Roivorth — Surface Geology of N. Europe. 259 



Central Eussia. How is it, then, that the asar did not continue 

 their strange march right away to these goals? Did the subglacial 

 rivers stop short where the various Swedish asar terminated their 

 journey? If so, what became of their water ? Was it frozen again ? 

 How was this ? The further south we travel, the warmer must the 

 climate have been under the same conditions, and consequently the 

 more water must have flowed from the ice-sheet. Its drains, the 

 subglacial rivers, must therefore have increased in volume instead of 

 dying out, and surely when they reached the flat country of Poland 

 and Russia must have become more and more liable to deposit 

 materials in their beds. How is it, th'en, that the asar do not 

 continue their march to Cracow ? But apart from all this, let me 

 repeat a question I have already asked, and which presents itself to 

 a traveller who has crossed the country in a very grotesque fashion. 

 I wonder if the champions of subglacial rivers as the depositors of 

 the asar have ever drawn a series of contour-lines, say from 

 Dalecarlia to Silesia, and if so, how do they propose to explain 

 the flow of any river, whether under an ice arch or not, along such 

 a course, not only across the undulating surface of Sweden, but 

 across the Baltic depression ? 



There remains another element which we have not yet considered, 

 namely, the large, sometimes portentously large, angular and sub- 

 angular blocks which occur in the surface layers of the asar, and 

 sometimes in large numbers on their backs, the as near Gamla 

 Upsala being a good example. Among the many boulders we 

 noticed, there was one whose cubical contents must have been 

 36 yards. Similar subangular and angular blocks have occurred in 

 the deposit containing marine shells at Upsala. How are we to' 

 explain these blocks and their occurrence where they are found, by 

 any kind of fluvial action ? Rivers must become desperate torrents, 

 such as occur sometimes in the ravines of the Caucasus and the 

 Western Himalayahs, to move such stones at all, and how could 

 they be deposited by rivers in the midst of stratified sands with 

 marine shells, and on the tops of the asar ? How comes it they are 

 not found at the bottom, where the cannon-shot gravel so often 

 occurs ? When it is said they were transported by ice-rafts, how 

 could they get on to the backs of the ice-rafts ? If frozen to their 

 under surface, the difficulty is still greater, for torrential rivers do 

 not freeze into solid masses, nor does their ice-covering become 

 attached to boulders which may be lying on their beds. So far as 

 I know, rivers in Scandinavia do not now carry about and deposit 

 such stones, except when there may be an occasional collapse in 

 their banks ; and if the glacial rivers derived them from dis- 

 integrated banks, it only removes the difficulty of their explanation 

 one step further back. But those who appeal to ice in this fashion 

 forget the relative age generally assigned to the surface beds of the 

 asar. The great majority of geologists are emphatic about the 

 surface beds of the asar containing marine shells being Post-Glacial. 

 If so, then we have a double crux, for not only have we to explain 

 the existence of gigantic erratics far away from their parent beds, 



