ANNIVERSARY ADDRESS OF THE PRESIDENT. CXXX1 



as a general rule, there is not a greater extension of a distorted fossil 

 in the line of the dip than in that of the strike of cleavage. 



Glaciers. — The researches of Professor Tyndall on the properties of 

 ice and the phenomena of glaciers having been alluded to in the pre- 

 ceding remarks, it seems to me desirable to offer a few observations on 

 that interesting subject ; for, though glaciers are not at present recog- 

 nized as having at a comparatively recent epoch extended their action 

 over a vast extent of the earth's surface, plain as well as moun- 

 tain, they have been still more intimately connected with the general 

 history of the earth, by the researches made, especially by Professor 

 Ramsay, to detect traces of their past action, not merely on ancient 

 rocks, but within the periods during which such rocks were deposited. 

 The great difficulty in accounting for the progressive movement of 

 glaciers, is to provide a sufficient force to put such ponderous masses 

 into motion, and to keep it up notwithstanding the retarding force 

 of friction. Some of the earliest investigators, as Saussure, con- 

 sidered the force of gravity as sufficient to produce motion, whilst 

 the melting of the ice in contact with the earth reduced the friction 

 to a minimum, or, in the words of Mr. Mallet, placed as it were liquid 

 rollers under the ice. Anterior, however, to this mode of explana- 

 tion, the • Swiss philosopher, John Jacob Scheuchzer had advanced 

 a totally different one in his ' Itinera per Helvetise alpinas regiones,' 

 a work which was published by Yaudon of Leyden, in 1723, and 

 dedicated to Sir Isaac Newton, then President of the Eoyal Society, 

 of which Scheuchzer was a member. Scheuchzer observes that the 

 movement of glaciers requires not to be explained by any miraculous 

 agency, but is entirely dependent upon natural causes ; for he adds, 

 " Solet nempe aqua a tergo montium rupiumque glacialium denuens, 

 vel in fissuris ipsis et interstitiis aliis glacialibus collecta, et utrobique 

 conglaciata, quoiflam amplius in hoc statu requirit spatium (con- 

 testantibus id experimentis circa frigus et glaciem institui solitis), 

 undiquaque premere et earn quidem glaoiei partem quae liberum 

 aerem respicit, et pascua declivia actu ipso propellere, et una cum 

 glacie arenam, lapides, saxa etiam grandiora, quo ipso hyperbolica 

 ilia purgatio simul explicari et facile intelligi potest." All will 

 remember the ingenious manner in which Agassiz, following Char- 

 pentier, adopted and applied this theory, by assuming that a multi- 

 tude of capillary cracks are formed at night, — that water produced by 

 the melting of the ice on the surface by the sun's rays during the day 

 filters into the cracks, and is frozen and therefore expanded at night, 

 when, by the expansive force of so many frozen seams of water, the ice 

 is put in motion, new cracks are formed, and all is ready for a repe- 

 tition of the same results. This theory was at first as popular as the 

 simple gravitation-theory had at first been, when Professor James 

 Forbes, considering it too hypothetical, entered upon the investigation 

 of the subject, and, after most laborious personal researches in the 

 Alps, guided and supported as they were by the light and vigour of 

 his philosophical mind, brought forward facts and reasonings not 

 merely to overthrow the hypothesis of Agassiz, but to prove that, 

 however difficult it may be to reconcile the motion and the other 

 phenomena of glaciers with the gravitation-theory so long as the 



