PRIMARY LIMESTONE. 367 



they cannot be thus distinguished in hand speci- 

 men ; when it becomes unavoidably necessary 

 to have recourse to their geological connec- 

 tions. 



In concluding this subject, it must finally be 

 remarked, that, if the limestones supposed to 

 appertain to the transition class, be referred to 

 the secondary, those which are decidedly pri- 

 mary, and which alternate with the several strata 

 already described, will be found to occupy a very 

 small space in nature, when compared to them. 

 Should even many of the transition limestones of 

 geological writers, prove to be strictly primary, 

 this rock will still bear a small proportion to the 

 other substances of this class ; and, in this re- 

 spect, a strong contrast may be observed between 

 the primary and secondary classes, in the last of 

 which limestone takes so conspicuous a share. 

 The geological considerations arising out of this 

 fact, are of a highly interesting nature. 



