AND ANALOGIES, OF ROCKS. 229 



cement ; whereas most of the local rocks of this 

 character consist of one or more sorts of fragments 

 united by a third cementing substance, or by a cement 

 composed of one of the imbedded ingredients. The 

 local conglomerates rarely occupy any considerable 

 space, and are often very limited ; while they are 

 always attached to some simple or compound rock 

 with which, in some parts, they are intimately united. 



As the general conglomerates constitute a separate 

 and independent set of strata, the local rarely form 

 more than one bed, and are sometimes not even 

 found in the shape of a bed ; constituting a single 

 lamina only, adhering to a parent rock, or an irre- 

 gular mass, in some other way connnected with it. 

 The general ones frequently contain rounded masses, 

 but the fragments of the local are commonly angular, 

 or little affected by attrition. In many instances 

 they are perfectly acute ; while, occasionally also, 

 when of large size, they are found to be so little 

 moved from their places, or separated from each 

 other, that the imagination easily replaces the de- 

 tached parts. 



These rocks have been sometimes distinguished by 

 the name of Breccia, while the others have been 

 called pudding stone ; but as the term Breccia has 

 also been very indiscriminately used, it is not con- 

 venient to perpetuate its application where it is neces- 

 sary to be accurate. Circumstances occasionally vi- 

 sible in the secondary strata, and more particularly in 

 the calcareous, will explain the origin of the local 

 conglomerates. 



The beds of these are often found covered on the 

 surface by their own fragments, intermixed with mi- 

 nuter particles of the same, or of clay. The inia- 



