484 Mr, J. Ball on the Structure of Glaciers. 
thickness arid appearance of the névé beds, their unequal ylaeis 
fication, and the fact that while, at intervals, some are clearly 
defined to the eye by a dark line along the outcropping edge of 
their upper surface, the greater number are but very faintl 
traced. The dark lnes betray the increased effect of the wind 
during long intervals of fine weather in summer, when larger 
surfaces of earth and rock are exposed, small particles of which, 
with dead insects, leaves, &c., are then carried far and wide over 
the smooth and crisp snow-plains. 
Passing from this point, I would wish to fix attention on the 
fact, that while all observers admit the stratification of névé, no 
one of those who believe that all trace of that original structure 
disappears in the next stage of its existence—the glacier ice of 
the middle region—has attempted to account for so extraordinary 
and, as far as I know, so unique a fact, as the utter destruction 
of all trace of the internal arrangement of vast masses of matter. 
Granting the possibility that pressure and movement combined 
may effect such a result, it would be most desirable to obtain 
some insight into the modus operandi, and, if possible, to detect 
the process in Nature’s own laboratory. 
Until some approach has been made to clearing up this my- 
stery, either by well-devised experiments, or by successful de- 
scents into some of the great crevasses of the upper regions of 
the glaciers, it can scarcely be said that our knowledge of glacier 
structure is complete. 
Professor Forbes has indeed asserted, in more than one pass- 
age of his writings, that all traces of structure, including as 
well the vemed structure of the middle and lower region, as the 
stratification of the névé, are utterly destroyed in the ice-cataracts 
that occur on many glaciers when the frozen stream is forced 
down a steep declivity. With all respect for so great an autho- 
rity, I have never been able to accept this statement, and my 
incredulity was recently confirmed by a rather careful observa- 
tion of the ice-cataract of the glacier of Rosenlani. Confining 
myself, of course, to those falls where the continuity of the 
glacier is not interrupted, the whole mechanical effect upon the 
mass of the glacier is simply to cause the production of many 
deep and wide crevasses, or, very frequently, of a double system 
of crevasses, breaking up the superficial portion of the ice into 
trregular quadrilateral prisms. As the whole mass advances, 
wasting of the ice takes place along the exposed surfaces, but 
especially on those that are most affected by the sun, and so the 
prisms become narrowed upwards and obliquely cut away on 
one side. When the glacier stream reaches a gentler slope at 
the foot of the fall, and flows over a concave, instead of a con- 
‘yex bed, the sides of adjacent prisms are brought nearer to each 
