!848. 



GENESEE FARMER. 



293 



thickness of loose snow, which completely hides them from 

 observation, exposing the traveller to the risk of certain 

 destruclion should he inadvertently happen to cross their 

 track. To this, however, the native guides have become 

 accustomed, and their ready and practical eye detects at 

 once a .slight depression on the smooth and unbrokerf sur- 

 face of the snow, as sketched below, a showing the depres- 

 eion of surface indicating the fissure beneath. 



Over these exicnsi\( Llit.crbUL ('. i j\c. i;ine u! the 

 wildest and most fantastic natural formations imaginable 

 Frequently we find an immense 

 boulder resting on the top of a 

 pillar of ice, and the beholder 

 is astonished at the singular 

 sight of an immense rock at a 

 considerable elevation above 

 the surface of the glacial forma- 

 tion supported by a single slen- 

 der shaft of ice some ten or fif- 

 ~ "f ; teen feet in height. 

 ' '"'/ This is easily explained by 



' "' ~-~~ " — — ^ simply observing that as the ice 



melts above or around one of these isolated boulders lying 

 originally on or beneath the surface, the rock itself protects 

 the ice "underneath it from melting, until in a process of 

 years the surrounding ice becomes gradually melted away, 

 leaving the boulder in its former position until the gradually 

 diminishing support fails, and it fills with a tremendous 

 crash again to the surface. 



Another feature of the glaciers is this, the rivulets before 

 mentioned carry with them larpo masses of loam arid sand, 

 wit'i which the snow and ice from the mountain sides fre- 

 quently abounds, and by their constant acwnnulation and 

 deposit in the fissures fill the opening with the earthy mat- 

 ter, after which, in the same manner as before described, 

 the ice dissolves gradually around it and leaves it in the 



— ,^. form as represented below, the 



■^^-W^ -39 dotted lino representing the 



^;^f. _ ^_^ original surface of the ice, a 



* ^ tlie mass of accumulated sand 



above the surface partly imbedded in the crevice of ice, and 

 //, the ice that remains still undissolved ; this, however, in 

 the course of years also becomes melted and leaves the hil- 

 -^ lock or mound of sand thus, 



C \ which is of a geological char- 



acter entirely different from 

 5 the soil of the valley where it 

 is deposited. 



It hag, however, been proven that this vast plain of ice 

 does not melt equally over the extent of its surface, but the 

 sides being in contact with the rocks and cliffs of the moun- 

 tains, the rocks being warmed during the day above the 

 surrounding temperature and retaining their heat during the 

 evening and a part of the night, will -ontinue to dissolve 

 the ice on the sides of the valley after it has ceased melting 

 in the center, by which process it frequently assumes this 

 form. 



Mountain 



This, the Professor said, had been fully demonstrated 

 where the sides of the valley were equally exposed to the 

 rays of the sun, and in other cases where the valleys were 

 so situated as to receive the sun on one side only, while the 

 other was shadowed by mountains, he had always observed 

 that the surface of the ice in the valley presented the fol- 

 fowing form ; a representing the peak shadowing the val- 

 ley, h the ice as the surface was acted upon by the sun's 

 rays, and c the sunny side of the valley showing the glacier 

 nearly dissolved on that side. 



The waste of ice in the summer is very considerable, 

 varying from 5 to 10 feet, according to the exposure of its 

 surface to the sun's rays. 



One of the striking and wonderful phenomena of the gla- 

 ciers is their constantly progressive movement, which is 

 annually from 180 to 250 feet. 



Although it has been a well known fact that these im- 

 mense beds of ice were not stationary, it had never been 

 known at what rate this movement was going forward, 

 until the lecturer, assisted by some of the best topographical 

 engineers and most scieniific men of Switzerland proved by 

 their experiments and discoveries during ten years of care- 

 ful investigation the facts as before related, viz. that the 

 average progress is about 250 feet per annum in the middle 

 of the valley, while at the sides the progress was compara- 

 tively slow. 



Their metliod of ascertaining these facts was as follows, 

 viz : they commenced their survey of one of the glaciers 

 extending over a valley of about 5,000 feet in width. The 

 first operation was to plant in the ice a straight line of poles 

 directly across this ice covered valley thus : 



On their return the ensuing summer the poles or stakes 

 had assumed the following position, those in the middle 



'^ZZ^ 



having advanced 250 foot, while those on the borders had 

 progressed on one side only seventeen feet and on the other 

 twenty. On each successive year the measurement was 

 acurately taken and the progress of the glaciers was as fol- 

 lows : the curved line marking the position of the sticks or 

 poles originally placed in n direct line, as at a, and b the 



position the second year, c the third, d the fourth year, and 

 so on through eight or ten year's observation. 



These glaciers are generally, as before stated, covered 

 and intermingled with immense quantities of loose rocks 

 and boulders, detached originally from the rocky cliffs and 

 sides of the mountains, which are forced onward with these 

 vast bodies of ice over the frequently irregular surface of 

 the valleys containing more or less of similar rocks from the 

 mountains, which may be illustrated by the following dia- 

 gram of a section of one of these valleys yvith the glacial 

 formation entirely covering its surface. This immense body 



of frozen snow and ice, sometimes to the depth of a thou- 

 sand feet, moves forward in the manner described, from 100 



