254 THE POPULAR SCIENCE MONTHLY. 



the tidal currents with an unfailing supply of muddy sediment. 

 It is mainly in the erosion, transportation, and reprecipitation of 

 these two rocks, and especially of the latter, that the process of 

 marsh formation consists. The incessantly destructive tide-work 

 may be seen at many points along the shore line, perhaps most 

 conspicuously at the base of Blomidon. Here the sandstone 

 foundation is continuously being cut away from under the super- 

 incumbent columnar trap ; and at intervals, especially in the 

 spring time, large masses of the igneous rock are loosened from 

 the precipitous mountain side and crushed upon the beach below, 

 where the solvent and abrading action of the waters can reach 

 them. It is after one of these spring slides that the richest har- 

 vests of amethystine and zeolitic crystals, for the beauty and 

 abundance of which the Minas shores are noted, can be secured. 

 But it is along the bottom of the bay that the destructive tidal 

 work is most extensive and effective. Here exist great troughs, 

 furrowed out of the soft sandstone, many fathoms deep along the 

 channel bed, with here and there the interruption of the trans- 

 verse trappean dikes already spoken of. 



The sandstone yields, of course, the greater part of the marsh- 

 creating sediment. Its detritus consists of a large percentage of 

 silica, a little clay, the iron which mainly determines its reddish 

 color, and the calcareous matter which served as cement in the 

 parent rock. This material, in the extremely comminuted form 

 in which it occurs in marsh-land soil, would itself afford condi- 

 tions highly favorable to the support of vegetable life. But an 

 additional cause of the wonderful fertility of the Acadian marshes 

 is the richness of the trap rock in various salts of potash, lime, 

 and alumina which the action of the water mingles freely with 

 the sandstone mud. The plant-supporting power of this complex 

 soil is increased still further by contributions from the upland 

 soils through the medium of the streams and rivers flowing 

 toward the bay. 



The great fertility of this alluvium may be inferred from the 

 fact that portions of the Annapolis, Cornwallis, Grand Prd, and 

 Cumberland marshes have been producing annually for nearly 

 two centuries from two to four tons per acre of the finest hay. 

 Besides, it is a common practice, after the hay has been removed, 

 to convert the marshes into autumn pastures, on the luxuriant 

 tender after-growth of which cattle fatten more rapidly than on 

 any other kind of food. Thus, virtually, two crops are annually 

 taken from the land, to which no fertilizing return is ever made. 

 The only portions of the Acadian marshes that have as yet 

 shown signs of exhaustion are those about the Chiegnecto branch 

 of the bay, on the cliffs and bed of which the Triassic rocks do 

 not occur, but in their stead a series of blue and gray "grind- 



