138 



POPULAE SCIEISrOE N"EWS. 



[September, 1888. 



r ■ 'n ' ? ^^J^'^Wi^^?*^ii^^ bjaiKas 



AN IMMENSE BOWLDER. 



The accompanying engraving is from a 

 photograph by Dr. Lortet, published in La 

 Nature., of an immense block of stone poised 

 upon the surface of the Gorner glacier in 

 Switzerland. It is doubtless a familiar fact to 

 most of our readers, that these glaciers are 

 really rivers of ice in constant motion, flowing 

 down the sides of the Alps and through the 

 valleys. The motion is slow — only a few 

 inches a day at the most — but irresistible; 

 and, as the glacier moves through its rocky 

 channel, its surface becomes covered with dirt, 

 stones, rocks, and all manner of rubbish which 

 fall upon it from above, or are broken off from 

 the sides of the valley by its own movement. 

 Many of these rocks are carried down to the 

 lower end of the glacier, and left heaped up 

 as it melts, form- 

 ing what is known 

 as the terminal 

 moraine. Others 

 fall into crevasses 

 in the ice, and are 

 ground up into 

 sand and clay by 

 the glacier itself, 

 and carried off in 

 the stream of 

 water which flows 

 from it. 



The large block 

 of stone shown in 

 the engraving is a 

 mass of gneiss 

 brought by the 

 glacier from Monte 

 Eosa. It is ele- 

 vated about one 

 hundred and 

 twenty feet above 

 the general surface 

 of the glacier, 

 owing to an un- 

 evenness of the ice. 

 The visible part of 

 the bowlder measures thirty-nine feet in height, 

 thirty-three feet in widtli, and nine feet in 

 thickness, so that this single stone contains 

 nearly twelve thousand cubic feet. The 

 greater part of the stone, however, is buried 

 in the ice ; and a piece of nearly equal size 

 has at some time been split off from it, and 

 is shown in the engraving lying on the rocks 

 below. The original stone, therefore, must 

 have been two or three times larger than the 

 part now visible on the glacier. 



The traces left by a glacier as it passes over 

 the surface of the earth are ver^' characteristic. 

 The rounded stones and bowlders, the polish- 

 ing, grooving, and scratching of the underly- 

 ing ledges, the immense deposits of gravel, 

 sand, and clay, all show where the glacier has 

 been at work. They can be traced down the 

 Swiss valleys far beyond the points to which 

 they extend at present, and out upon the 

 plains of central Europe. The only glaciers 

 in this country are a few in the northern part 

 of the Rocky-Mountain range ; but the evi- 



dence is indisputable, that, at some distant 

 period, the entire northern part of the country 

 was covered with moving ice, thousands of 

 feet in thickness. In some places the country 

 is almost covered with bowlders, brought by 

 the ancient glaciers from some distant moun- 

 tain-side ; and in Essex County, Mass., there 

 is one nearlj' equal in size to the more modern 

 bowlder of the Gorner glacier. These facts 

 seem almost incredible, but they are proved by 

 the strongest evidence ; and it is by no means 

 improbable, that, after many thousand j'ears, 

 the same conditions may again obtain, and 

 the ice cover the country once more, as it now 

 covers the land about the south pole of the 

 earth, and many parts of Greenland. 



Dr. Nichols, the former editor of this paper, 

 was greatly interested in the study of bowlder- 



rocks during his life ; and a large ice-hewn 

 stone, taken from his farm at Lakeside, now 

 marks his last resting-place. 



FERMENTATION. 



Fermentation is a peculiar ijrocess which 

 takes place in organic bodies in which chemical 

 change and decomposition occur under the 

 influence of certain nitrogenous substances 

 known as ferments. The ferments appear, in 

 most cases at least, to possess vitality, and 

 grow and increase in the fermenting substances 

 like plants or animals. 



The vinous or alcoholic fermentation is the 

 variety of the most importance. This fermen- 

 tation takes place in bread-making and the man- 

 ufacture of beer, wine, and spirits. It consists 

 in the decomposition of starch or sugar into 

 alcohol and carbonic-acid gas, under the in- 

 fluence of an organized substance known as 

 the j-east-plant. Although commonly called a 

 plant, it resembles rather more an animal, inas- 



much as it feeds upon complex substances, 

 breaking them up into simpler ones. A man 

 or a horse feeds upon starch, and excretes it 

 in part, in the form of carbonic-acid gas like the 

 yeast ; while a plant feeds upon the carbonic- 

 acid, and builds it up again into starch and 

 sugar. 



Starch will not ferment directly, but is flrst 

 converted into glucose, or grape-sugar. This 

 occurs in grain during the process of malting 

 or germination. A substance called diastase, 

 present in the grain, seems to determine this 

 change. Common cane-sugar, or saccharose, is 

 also unfermentable, but must first be changed 

 into grape-sugar, or glucose. 



Although yeast is usually introduced artifl- 

 ciall}- into the substance it is desired to fer- 

 ment, the cells are apparently present in the 



^^^^ air at all times, and 



~~-' I cause fermentation 



I to take place spon- 

 1 taneously when the 

 fermentable liquid 

 is freely exposed 

 to it. There is an 

 ; old question. 

 Where did the flrst 

 brewer get his 

 3'east ? which has 

 never been an- 

 swered; for, 

 although he un- 

 doubtedly obtained 

 it from the air, it 

 is hard to say 

 where the yeast- 

 cells present in the 

 air were flrst de- 

 veloped. The 

 extreme limits of 

 temperature at 

 which the yeast can 

 live are 41° and 86° 

 F., consequently 

 fermentation can 

 only take place 

 between these points. 



When yeast is introduced into a liquid 

 capable of fermentation, it begins to grow, 

 and throw out arms, until the surface of the 

 liquid is completely covered. This is known as 

 the harm, or surface yeast, while at the bottom 

 of the liquid a viscid sediment known as the 

 bottom yeast is deposited. The surface yeast 

 is used b}' bakers in raising their bread, and is 

 collected from the breweries daily, compressed 

 into small cakes, and extensively sold to 

 housekeepers under the name of Vienna yeast. 

 The barm is also used by the brewers for the 

 fermentation of the succeeding batch of beer. 

 The bottom yeast produces a slightly different 

 fermentation, and is used in the manufacture 

 of wines, and a variety of Bavarian beer which 

 does not sour b3' exposure to the air. 



It is a curious fact that during fermentation 

 the glucose is not entirely converted into alco- 

 hol and carbonic dioxide, but about three per 

 cent of the glucose is changed into ghcerine, 

 and 0.6 per cent into succinic acid. It has 



