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 5, 10, or 20 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 miles 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 first sight to disappoint a Swedish, Scotch, Welsh, or North American geologist. 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 from a similar scrutiny of the boulders and pebbles of the terminal moraine of one of the old extinct glaciers, namely, that of the Rhone in the suburbs of Soleure. Thus at the point K in the map, Figure 42, I observed a mass of unstratified clay or mud, through which a variety of angular and rubbed stones were scattered and a marked proportion of the whole were polished and scratched and the clay rendered so compact, as if by the incumbent pressure of a great mass of ice, that it has been found necessary to blow it up with gunpowder in making railway cuttings through part of it. A limestone of the age of our Portland stone on which this old moraine rests, has its surface polished like a looking-glass, displaying beautiful sections of fossil shells of the genera Nerinaea and Pteroceras, while occasionally, besides finer striae, there are deep rectilinear grooves, agreeing in direction with the course in which the extinct glacier would have moved according to the theory of M. Guyot, before explained. EXTINCT GLACIERS OF THE ITALIAN SIDE OF THE ALPS. [Illustration: Figure 43. Map Of The Moraines Of Extinct Glaciers] (FIGURE 43. MAP OF THE MORAINES OF EXTINCT GLACIERS EXTENDING FROM THE ALPS INTO THE PLAINS OF THE PO NEAR TURIN. From Map of the ancient Glaciers of the Italian side of the Alps by Signor Gabriel de Mortillet.