160 VISCOUS THEORY OF GLACIER MOTION. [184G. 



more obvious kinds are no longer proofs of genius and perspi- 

 cacity, 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 pro- 

 perties and organs have been studied with such persevering 

 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 maintained 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 possess imper- 

 fectly every quality admitting of degree ; when adamant is re- 

 jected from our vocabulary, and softness means only less hard- 

 ness, and the definition of a perfect fluid is as imaginary as that 

 of a solid without weight ; when a vacuum and a plenum are 

 alike scoffed at, and even the heavenly bodies toil through media 

 more or less resisting ; when no substance is admitted to ex- 

 pand uniformly by heat, when glass may be considered a con- 

 ductor 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 aggrega- 

 tion of freezing water and thawing ice 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 yield- 

 ing, moulding, self-adapting power, sufficient 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 compared, and calculated and mapped, and con- 

 firmed 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 



* [In the Atmospheric Railway.] 



