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SOME MODERN ROCK-BUILDING. 



By F. a. Dixox, M. A., Principal Sackville High School. 



When one takes a survey of the rock foundations of the 

 earth's crust, he is so impressed with their structure, — a process 

 so slow in its operation that time as measured by years or by 

 the life of man is too short to mark any perceptible progress in 

 the work, — that he is at tirst rather apt to assume the work as 

 complete than to look for evidence of present rock-building. 



But rocks are being constructed now just as truly as at any 

 previous time in the earth's history. Streams overflowing their 

 banks in time of freshet leave a thin layer of sediment behind to 

 a dd to the depth of the intervale. Rivers carry down to their 

 lower courses and into bays and seas material washed from the 

 land, which material, down in the calm depths remote from our 

 observation, is deposited to become compressed in the course of 

 ages into solid rock. 



But the marshes at the head of the Bay of Fundy afford an 

 instance of rock-building of the present, at once unique in its 

 character and affording unexampled opportunity for observation. 

 Here the material is carried from the bay inland up the rivers, 

 and is deposited on banks and other areas overflowed at high 

 water. The retreat of the tide permits examination of each 

 layer of deposit before the next is made, while at any time, ex- 

 cept that of high water, numbers of layers can be cut through 

 with the spade and an outcrop is then exposed. 



Nature's apparent eccentricity in thus carrying material from 

 lower to higher levels is the result of the excessive rise of tide 

 that here occurs, and which in turn is the result of the shape and 

 position of the Bay of Fundy. 



The extreme difference between low and high water levels 

 diflfersin different parts of the bay. It has been much exaggerat- 

 ed, and a rise of 60 feet of tide is 'commonly believed. This 

 height is greater by several feet than that actually occurring. At 

 the head of Cumberland Basin, the greatest difterence of level is 

 about 46 feet. In the Tantramar River, at the I. C. R., only a 

 few miles from the basin, the rise of tide is 35 feet, and a few 

 miles further up the same river, at the highway bridge at Upper 

 Sackville, the rise is 24 feet. 



