'2'2i\ y/i' ^\iii( I'icdit Orohif/lsf. ( )(t(jt)er, l*.a 
:iltiUHl;iiilly ami iiiori' uii*MHiall\ . In the ci'iitral part of the nhicicr 
most of the inoraiiiif material disappears clown the crevasses. Tiie 
ertect of the transition from smooth to rough iee <tn the appear- 
ance of the moraines is well shown on those which eonie down just 
to the west of 11. After a crevasse is formed the sun melts back 
its north wall rapidly, ([uickly converting a broad ridge of ice into 
a very sharj) one. changing the appearance of the ridges ([uickly. 
and causing most of the moraine load to be dropped. * 
Siirfacr Fcntiirrs prod 11(1(1 1)1/ ^[air Gl(tci(r. Sitrfacc j^ rod need 
on ridg(K (tt right (unjla^ to the )ii or cDtciif.— On all the mountain 
sloi)es which Muir glacier has overrun, a tendency toward the 
production of a surface consisting of small, shallow valley's sep- 
arated by low ridges is seen, both trending in the direction in 
which the ice has moved. This configuration of surface is most 
marked on narrow ridges whose long axes make an angle approach- 
ing 00° with the direction of ice movement. Nunatak G, the 
ridge between the Western l)ranch and the Dying glacier valley, 
and in a less degree the northerly spurs of ]Mt. ^^'right. present 
excellent examplest. The production of such surfaces in this 
region depends on the presence and distribution of the fissure 
planes. AVeathering takes place along these |)lanes to varying 
depths, resulting in the loosening of V shaped 1 docks of varying 
sizes. After such decay has l)een in progress for a considerable 
length of time, a glacier riding over the ridge and removing 
loosened material will tend to leave a surface c()nii)osed of ridge- 
like projections with shallow depressions l)etween. This will l)e 
the more marked the more nearly the trend of the fissures coin- 
cides with the direction of the ice. Such a surface could scarcely 
be produced if the angle l)etween these two was a considerable 
one. Even witliout the presence of the fissure jjlanes it is con- 
ceivable that there would be a tendency toward the production of 
such surfaces in regions where rock decay ha<l taken place to 
varying depths. But no such cause caul)e assigned here l)ecause 
the rapidity of disintegration prevents decay in i)lace. 
Ldk-cH. — On the tops of all the low mountains bordering ]VIuir 
* In respect to the size of its moraines Muir glacier* seems to be an 
exception to the generality of Alaskan glaciers that I have myself seen 
or have seen (lescribod.' Compare 1. C. Russell, Hull U. S. Geol. Sur. 
Vol. I, p. ir)l. 
|Just such surfaces are figured by John IVIuir in his paper in the re- 
port of the cruise of the Corwin in the Arctic ocean — IfSbo — on the 
glaciation of the region. 
