I is amation is far the vax is pantes he surfaces of which are places Í vena chesica: nd at by the pressure these re squeezed fat hus producing planes of veakness Imps to the pressure. 7. 3 the min ause of he deavage I take to be the later wing of the particles of wax over each Du attachments are thereby severed, which the new ones fail to make good. Thus the tangential sing prodness lamination, is the mis near a station are ausei o exitiate by the gilding of the wheel. 48. Instead of wax we may ake the slate itself, grind i o ine powder, add water, and thus reproduce the pristine mud. By the proper compression of such nud. in me firection, the cleavage is restored. 489. Cal now to mind the evidences we have had of the power of thawing ice to yield to pressure. Reec Leet the shortening of the Glacier du Géant, and the squeezing of the Glacier de Léchaud, at Trélaporte. Such a substance, slowly acted upon by pressure, will yield laterally. Its particles will slide over each other, the severed attachments being immediately made good by regelation. It will not yield uniformly, but along special planes. It will also liquefy, not uniformly, but along special surfaces. Both the sliding and the liquefaction will take place principally at right angles to the pressure, and glacier lamination is the result. 490. As long as it is sound the laminated glacier ice resists cleavage. Regelation, as I have said, makes the severed attachments good. But when such ice is exposed to the weather the structure is revealed, and the ice can then be cloven into tablets a square foot, or even a square yard in area. $67. Conclusion. 491. Here, my friend, our labours close. It has been a true pleasure to me to have you at my side so long. In the sweat of our brows we have often reached the heights where our work lay, but you have been steadfast and industrious throughout, using in all possible cases your own muscles instead of relying upon mine. Here and there I have stretched an arm and helped you to a ledge, but the work of climbing has been almost exclusively your own. It is thus that I should like to teach you all things; showing you the way to profitable exertion, but leaving the exertion to you-more anxious to bring out your manliness in the presence of difficulty than to make your way smooth by toning difficulties down. 492. Steadfast, prudent, without terror, though not at al times without awe, I have found you on rock and ce, and you have shown the still rarer quality of steadfastness in intellectual effort. As here set forth, ur task seems plain enough, but you and I know how ten we have had to wrangle resolutely with the facts being out their meaning. The work, however, is now lue, and you are master of a fragment of that sure derrain knowledge which is founded on the faithful udy of nature. Is it not worth the price paid for 15 Or rasher, was not the paying of the price—the ealthiul, if sometimes hard, exercise of mind and dy, upon alp and glacier-a portion of our delight? 193. Here then we part. And should we not meet ail, the memory of these days will still unite us. Se me your hand. Good bye. LONDON: PRINTED BY AND PARLIAMENT STREET |