242 THE JOURNAL OF GEOLOGY. 



from surface debris there would be no angular material left upon 

 the ridges when the ice finally disappeared. Such a system of 

 deposition as is sketched above would result in the formation of 

 narrow, winding ridges of cross-bedded sand and gravel, corre- 

 sponding, seemingly, in every way to the osars of many glaciated 

 regions. The process of subglacial deposition pertains especially 

 to stagnant ice sheets of the Malaspina type, which are wasting 

 away. In an advancing glacier it is evident that the conditions 

 would be different, and subglacial erosion might take place 

 instead of subglacial deposition. 



Alluvial cones. — Below the outlets of the tunnels through 

 which Malaspina glacier is drained, there are immense deposits 

 of bowlders, gravel, sand, and mud which have the form of seg- 

 ments of low cones. These deposits are of the nature of the 

 " alluvial cones," or " alluvial fans " so common at the bases of 

 mountains in arid regions, and are also related to the " cones of 

 dejection," deposited by torrents, and to the subaerial portion of 

 the deltas of swift streams. As deposits of this nature have not 

 been satisfactorily classified, I shall for the present call them 

 " alluvial cones." 



As stated in speaking of osars, the streams issuing from tun- 

 nels in Malaspina glacier at once begin to deposit. The larger 

 bowlders and stones are first dropped, while gravel, sand and 

 silt are carried farther and deposited in the order of their 

 coarseness. The deposits originating in this way have a conical 

 form, the apex of each cone being at the mouth of a tunnel. As 

 the apexes of the cones are raised by the deposition of coarse 

 material, their peripheries expand in all directions, and as the 

 region is densely forest covered, great quantities of trees become 

 buried beneath them. As the ice at the head of an alluvial cone 

 recedes, the alluvial deposit follows it by deposition on the up- 

 stream side. The growth of the alluvial cones will continue so 

 long as the glacier continues to retreat, or until the streams 

 which flow over them have their subglacial courses changed. The 

 material of the alluvial cones is as heterogeneous as the material 

 forming the moraines on the border of the glacier, about which 



