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GEOLOGICAL MEMOIRS. 



From the consideration of the general characters of ice and the 

 different forms of the important snow and " firn" beds that consti- 

 tute the earliest conditions for the formation of glaciers, we are next 

 led to the subject of the Topography of Glaciers proper. The glaciers 

 of the Alps are mostly assembled in extensive groups in the neigh- 

 bourhood of the most considerable elevations. According to their 

 extent and the regularity of their forms they have been divided into 

 the first or second order of glaciers, or primary and secondary ; there 

 is, however, a natural series of intermediate degrees. Those glacier 

 groups that lie on the declivities beside a larger one, constituting 

 glaciers of the second order, as well as forming the sources of the 

 larger glacier, have been also termed lateral glaciers. The gla- 

 ciers of the first order, on account of their extent and of the greater 

 scale on which they exhibit all the peculiar pheenomena of glaciers, 

 are more particularly adapted for special examination. MM. Schla- 

 gintweit have, therefore, for the most part confined themselves to a 

 full topographical survey of such of the larger glaciers, as those of 

 Pasterze, and the Oetz valley ; giving only occasional details of the 

 phsenomena of the lateral glaciers, particularly those of the Oetz 

 valley, as Vernagt, Hintereis, &c. In the third chapter (pp. 48-76) 

 the authors proceed to explain the details of the two elaborate charts 

 of the above-mentioned larger glaciers, accompanying the volume, 

 and the instruments used in making their observations, and to treat 

 of the general extent of glaciers. The measurements of the Pasterze 

 and of the Oetz-thal glaciers follow, with descriptions of their cha- 

 racters and external forms, illustrated with coloured lithographic 

 sketches and numerous woodcuts, their sources, and moraines, and 

 observations on single and compound glaciers, the origin of rock- and 

 firn-moraines, &c. The results arrived at are :■ — 1 . the formation of 

 glaciers is a very general phsenomenon in great mountains, and is 

 not only brought about by certain conditions of temperature and at- 

 mospheric moisture, but also by the peculiar formation of the valleys : 

 — 2. the least mean inclination of a glacier is 3° ; for glaciers of the 

 first order 5° to 7° is the inclination from their lower to their upper 

 extremity, including their "fini-meer" : — 3. in an alpine valley occu- 

 pied by a glacier, the following conditions obtain : the glacier proper — 

 hard ice ; the widely-extended " firn-meer" — granular snow ; both 

 are slightly inclined, and are intimately connected together. The 

 sides of the surrounding mountains are covered with summit-ice and 

 summit-snow [Hocheis and Hornerschnee, forms peculiar to very 

 great elevations], which are really separated from the "firn-meer" 

 by deep circular crevasses (" Bergschrunde" and " Rimayes") : — 

 4. every larger glacier has several sources, the separations of which 

 are marked by superficial lines of stones (stone-moraines), or by ex- 

 tended deposits of masses of " fim"-ice. In chapter iv. (pp. 77-101) 

 M. H. Schlagintweit describes the Intimate Structure of Glaciers, 

 noticing the arrangement of the lines and bands on the surface and 

 in the interior, also the dirt-bands, and the crevasses and ravines in 

 the ice ; and in the fifth chapter (pp. 104-124) he enters upon the 

 subject of the Motion of Glaciers, describing his method of observa- 



