.552 ISLE OF MAN. GEOLOGY. LIMESTONE. 



the conglomerate, taking place at the points where the 

 change occurs. 



It will hereafter be seen that the limestone beds in 

 Derby haven which are continuous with these, come into 

 contact with the primary strata without the intervention of 

 the conglomerate. It is therefore apparent that the bed 

 here described is of a very partial nature, and it may be 

 conjectured to diminish in a wedge-like form till it dis- 

 appears. It presents an example, analogous to those 

 cases occurring in Sky and elsewhere, of the extenuation 

 and disappearance of the lowest secondary strata, and of 

 the consequent contact of a superior set with the primary 

 rocks. 



IT is now necessary to proceed to the examination of 

 the limestone, being the uppermost of the stratified rocks 

 found in the island.* Its general extent is already un-* 

 derstood, from the topographical description which has 

 preceded, and from the accompanying map. However 

 different in mineral character the stratified and the un- 

 stratified limestone may seem to be, there will be sufficient 

 proof in the course of this examination that they are only 

 different parts of one common deposit. At the same time 

 this examination will throw light on many obscure points 

 in the history of the unstratified limestones. 



By far the greater portion of this limestone is disposed 

 in thin beds, in a parallel manner. The thickness of these 



* It is here proper to remark that many beds of' breccia are found 

 connected with this calcareous deposit, and occasionally, superior in 

 position. But these are of a partial nature, and are no where of such 

 extent or importance as to interfere with the claims of the limestone to 

 the rank here assigned to it. In other respects the perpetual inter- 

 ference of the diiferent breccias with the limestone, renders it impossi- 

 ble to describe the latter without occasionally adverting to these. It 

 will hereafter be necessary, even at the risk of some repetition, to collect 

 the whole of them into one general view. 



