22 THE MODERN PERIOD. 



tide : its retreat commences, and the waters rush back as rapidly as 

 they entered. 



The rising tide sweeps away the fine material from every exposed 

 bank and cliff, and becomes loaded with mud and extremely fine sand, 

 which, as it stagnates at high water, it deposits in a thin layer on the 

 surface of the flats. This layer, which may vary in thickness from a 

 quarter of an inch to a quarter of a line, is coarser and thicker at the 

 outer edge of the flats than nearer the shore ; and hence these 

 flats, as well as the marshes, are usually higher near the channels 

 than at their inner edge. From the same cause, — the more rapid 

 deposition of the coarser sediment, — the lower side of the layer is 

 arenaceous, and sometimes dotted over with films of mica, while the 

 upper side is fine and slimy, and when dry has a shining and polished 

 surface. The falling tide has little effect on these deposits, and hence 

 the gradual growth of the flats, until they reach such a height that 

 they can be overflowed only by the high spring tides. They then 

 become natural or salt marsh, covered with the coarse grasses and 

 Cai^ices which grow in such places. So far the process is carried on 

 by the hand of nature; and before the colonization of Nova Scotia, 

 there were large tracts of this grassy alluvium to excite the wonder 

 and delight of the first settlers on the shores of the Bay of Fundy. 

 Man, however, carries the land-making process farther ; and by diking 

 and draining, excludes the sea water, and produces a soil capable of 

 yielding for an indefinite period, without manure, the most valuable 

 cultivated grains and grasses. Already there are in Nova Scotia more 

 than forty thousand acres of diked marsh, or " dike," as it is more 

 shortly called, the average value of which cannot be estimated at less 

 than twenty pounds currency per acre. The undiked flats, bare at low 

 tide, are of immensely greater extent. 



The differences in the nature of the deposit in different parts of the 

 flats, already noticed, produce an important difference in the character 

 of the marsh soils. In the higher parts of the marshes, near the chan- 

 nels, the soil is red and comparatively friable. In the lower parts, 

 and especially near the edge of the upland, it passes into a gray or 

 bluish clay called " blue dike," or, from the circumstance of its con- 

 taining many vegetable fragments and fibres, " corky dike." These 

 two varieties of marsh differ very materially in their agricultural value. 

 It often happens, however, that in the growth of the deposit, portions 

 of blue marsh become buried under red deposits, so that, on digging, 

 two layers or strata are found markedly different from each other in 

 colour and other properties ; and this change may be artificially pro- 

 duced by digging channels to admit the turbid red waters to overflow 

 the low blue marsh. 



