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PEOFESSOES TT^'DALL AXD HEXLET OX 
viscosity. It may, however, be remarked, that the slight and irregular variations to 
which Professor Foebes alludes, and which are such as would occur if the motion were 
such as we suppose it to be, are likely to throw much hght upon the problem. It is 
also extremely probable that the motion, if eliected in the manner referred to, will be 
sometimes accompanied by an audible crackling of the mass. To this we paid but little 
attention when on the ground ; for the significance of this as well as of many other points 
was first suggested by the experiments made after our return. It is, however, we beheve, 
a phenomenon of common occurrence. Professor Foebes calls the glacier a “crackling 
mass he speaks of the ice “ cracking and straining forwards and in that concluding 
passage of his ‘Travels’ which has excited such general admiration, he says of the glacier, 
“it yields groaning to its fate.” Other observers make use of similar expressions. 
M. Desoe also speaks of the sudden change of the colour of the blue veins of the ice 
where a portion of the central moraine near the Abschwung is cleared away ; the obser- 
vation is very remarkable. “ Au moment,” says M. Desoe, “ ou on la met a decouvert. 
la glace des bandes bleues est parfaitement transparente, I’ceil y plonge jusqu’a une pro- 
fondeur de plusieurs pieds, mais cette purete ne dure qu’un instant, et Ton voit bientot 
se former des petites felures d’abord superficielles, qui se combinent en reseau de maniere 
a enlever peu a peu a la glace bleue toute sa transparence. Ces felures propagent egale- 
ment dans les bandes blanches, et lorsqu’on approche I’oreille de la smTace de la glace, 
en entend distinctement un bruit de crepitation qui les accompagnent au moment de 
leur formation.” These facts appear to be totally at variance with the idea of viscosity. 
In a chapter on the “ Appearance of the larger Glaciers,” in an interestmg little work 
by M. Moussox of Zurich, for which one of us has to thank the kindness of Professor 
Clausius, the phenomena which they exhibit are thus described * : — “ The appeai’ance 
of a large glacier of the first order has been compared, not without reason, with that 
of a high swelled, and suddenly solidified stream. It winds itself in a similar manner 
through the curving of the valley, is deflected by obstacles, contracts its width, or spreads 
itself out In short, the form is modified in the most complete manner to suit the 
character and irregularities of its bed. To this capacity to change its form, the ice of 
glaciers unites another property, which reminds us of the fluid condition ; namely, the 
capability of joining and blending with other ice. Thus we see separate glacier branches 
perfectly uniting themselves to a single trunk ; regenerated glaciers formed Aom crushed 
fragments ; fissures and chasms closed up, and other similar appearances. These pheno- 
mena evidently point to a slow movement of the particles of which the glacier consists ; 
strange as the application of such an idea to a solid brittle mass such as glacier ice may 
appear to be. The solution of this enigma constitutes one of the most dilRcult points in 
the explanation of glaciers.” 
'WTien the appearances here enumerated are considered with reference to the experi- 
ments on the regelation of ice above described, the enigma referred to by the writer 
appears to have received a satisfactory solution. The glacial valley is a mould tlirough 
* Die Gletscher des Jetztzeit, by Albert Mobsson. Zurich, 1854. 
