o04 ANCIENT AND MODERN GLACIERS CONTRASTED. CHAP. xv. 



stamped the lithological character of its own mountainous 

 region upon the lower part of its hydrographical basin by- 

 covering it with its peculiar Alpine drift. In like manner the 

 old extinct glacier of the Limmat, during its gradual retreat, 

 has left monuments of its course in the Lake of Zurich in the 

 shape of terminal moraines, one of which has almost divided 

 that great sheet of water into two lakes. 



The ice-work done by the extinct glaciers, as contrasted 

 with that performed by their dwarfed representatives of the 

 present day, is in due proportion to the relative volume of the 

 supposed glaciers, whether we measure them by the distances 

 to which they have carried erratic blocks, or the areas which 

 they have strewed over with drift, or the hard surfaces of rock 

 and number of boulders which they have polished and 

 striated. Instead of a length of five, ten, or twenty miles 

 and a thickness of 200, 300, or at the utmost 800 feet, those 

 giants of the olden time must have been from 50 to 150 miJes 

 long, and between 1000 and 3000 feet deep. In like manner 

 the glaciation, although identical in kind, is on so small a 

 scale in the existing Alpine glaciers as at fii'st sight to dis- 

 appoint a Swedish, Scotch, Welsh, or Xorth American geolo- 

 gist. When I visited the terminal moraine of the glacier of 

 the Rhone in 1859, and tried to estimate the number of 

 angular or rounded pebbles and blocks which exhibited glacial 

 polishing or scratches as compared to those bearing no such 

 markings, I found that several thousand had to be reckoned 

 before I arrived at the first which was so striated or polished 

 as to differ from the stones of an ordinary torrent-bed. Even 

 in the moraines of the glaciers of Zermatt, Viesch, and others, 

 in which fragments of limestone and serpentine are abundant 

 (rocks which most readily receive and most faithfully retain 

 the signs of glaciation), I found, for one which displayed such 

 indications, several hundreds entirely free from them. Of 

 the most opposite character were the results obtained by me 



