PLASTICITY — VEINED STRUCTURE. 
205 
Plasticity — Veined Structure. — I certainly never expected, when promulgating the 
viscous theory, that it would have met with so much opposition on the ground that 
the more familiar properties of ice are opposed to the admission of its plasticity; 
and that the fragility of hand specimens should be considered as conclusive against the 
plastic effect of most intense forces acting on the most stupendous scale upon a body 
placed in circumstances which subject it to a trial, beneath which the most massive 
constructions of the pyramid-building ages would sway, totter, and crumble. In 
an age when generalizations of the more obvious kinds are no longer proofs of genius 
and perspicacity, and when popular writers on science delight to startle their readers 
by showing how bodies the most dissimilar possess properties in common; in an 
age in which gradations of properties and organs have been studied with such perse- 
vering sagacity, and in which so many unexpected qualities have been discovered ;— 
when iron is classed as a combustible, when metals are found which float on water 
and which catch fire on touching ice, when a pneumatic vacuum is formed and main- 
tained in vessels five miles long, and whose sides are ripped open twenty times a day ; 
— when, moreover, the simpler abstractions of former times are being daily overset, 
when no body seems to possess any one property in perfection, and all seem to pos- 
sess imperfectly every quality admitting of degree ; when adamant is rejected from 
our vocabulary, and softness means only less hardness, and the definition of a perfect 
fluid is as imaginary as that of a solid without weight ; — when a vacuum and a ple- 
num are alike scoffed at, and even the heavenly bodies toil through media more or less 
resisting; when no substance is admitted to expand uniformly by heat, when glass 
may be considered a conductor of electricity, and metals as imperfect insulators ; — in 
these days, when the barriers of the categories are so completely beaten down, I had 
not expected to meet with so determined an opposition to the proposition that the 
stupendous aggregation of freezing water and thawingice, called a glacier, subjected 
to the pressure of thousands of vertical feet of its own substance, might not under 
these circumstances possess a degree of yielding, moulding, self-adapting power, suf- 
ficient to admit of slight changes of figure in long periods of time. Still less could I 
have anticipated that when the plastic changes of form had been measured and com- 
pared, and calculated and mapped, and confirmed by independent observers, that we 
should still have had men of science appealing to the fragility of an icicle as an un- 
answerable argument ! More philosophical surely was the appeal of the Bishop of 
Annecy from what we already know to what we may one day learn if willing to be 
taught : “ Quand on agit sur un morceau de glace, qu’on le frappe, on lui trouve une 
rigidite qui est en opposition directe avec les apparences dont. nous venons de parler. 
Peut-itre que les experiences faites sur de plus grandes masses donneraient d'autres re- 
sult ats*.” 
* Theorie des Glaciers de la Savoie, p. 84. Quoted in my Travels, p. 367, 2nd edit. Since this paper was 
read, Mr. Chrjstie, Secretary of the Royal Society, has kindly communicated to me a very striking remark 
upon a well-known and easily- repeated experiment. The experiment is this. If, in the course of a severe 
