364 PRIMARY LIMESTONE. 



proved, there is no reason to deny their probable 

 existence in the limestones of the same period ; 

 it is even certain, that, in one instance at least, 

 they do so occur. The crystalline texture is 

 equally incapable of proving their nature ; as it 

 is frequent in the secondary limestones, and is 

 not necessarily present in the primary. 



Primary limestone is found in strata of the 



usual variety of forms, alternating with other 



** 



rocks of the same class, and it occurs in every 

 part of the series. It exists, either in a consi- 

 derable succession of unmixed beds, or else in 

 rare and slender strata, or laminae intermixed in 

 small proportion with some other rock ; most 

 frequently, with the argillaceous schists. It is 

 also found in irregular masses, or large nodules, 

 which can scarcely be said to possess a stratified 

 shape, and which very much resemble, as already 

 remarked, the masses of serpentine that occur in 

 similar situations. Excepting in the crystalline 

 form, it is never found in veins ; and, in this re- 

 spect,, it is exactly analogous to quartz, the veins 

 of which are very similar, and generally found in 

 the Sime situations. 



