1 (30 The Ottawa Naturalist. 



difference in texture being probably due to more rapid crystallization 

 or cooling just as in the case of solutions of salt, sugar, alum &c, 

 where we find that the slower the cooling the larger the grain of the 

 crystal. These rocks, since they penetrated the oldest of the sedimen- 

 tary formations, by which term we mean those which have been laid down 

 by the action of water in some form may be regarded, as representing 

 in some cases at least, certain portions of the original mass or crust of 

 the earth. 



The sedimentary or aqueous rocks are composed largely of grains 

 of sand or often of pebbles, cemented together by sandy or calcareous 

 particles. These grains of sand and pebbles have been derived from 

 pre-existing rocks which in the first place presumably formed the first 

 floor, and which have been broken down and reduced by the action of 

 the elements, such as the force of waves, the rush of streams, the infil- 

 tration of rains or the action of frost. In addition to the beds of 

 sandstone and conglomerate, others, composed largely of calcareous 

 matter, in which the presence of organisms, as shells, plants, etc., can 

 be recognized ; as can be seen in the many quarries in the vicinity of 

 this city, where they extend over large areas, while yet others, com- 

 posed of fine material, such as mud and silt, now occur as shales, 

 and are easily recognized in the dark brownish or greyish material which 

 is dug up in many of our streets or seen along the banks of the Rideau 

 and Ottawa Rivers. 



The manner in which many of these sedimentary locks have been 

 produced can be readily seen by any one who has ever studied, in the 

 slightest degree, the action of water upon our sea coasts, lake shores, 

 or along our river courses. Thus it will be observed that a coast line 

 is generally composed of masses of rock jutting out here and there in 

 the form of cliffs or projecting points. These are separated by stretches 

 of beach or low shore in which rock ledges are frequently absent, but 

 which are composed of sand, gravel, mud, clay or boulders. These 

 have been produced by the long continued action of wave or current 

 against the rocky barriers, the force of which, by mechanical impact, 

 tends to break down the mass of the cliff into scattered blocks and 

 distribute them about its base. Subsequent rolling and dashing 



