THE HELM SD ALE STRATA. 433 



exclusively of Old Red Sandstone materials bound to- 

 gether by an Oolite cement, seem to represent periods 

 of great disturbance, during which the broken ruins of 

 some neighbouring coast composed mainly of the Caith- 

 ness Flagstones were spread to the depth of several feet, 

 and for great distances, over the previously quiet bottom. 

 And then another period of tranquillity took place, and 

 finely laminated shales were deposited over the rough 

 breccia until another paroxysm of violence overspread 

 them also with a breccia as rough as the underlying 

 one. And thus during a very protracted period the 

 process of alternate formations quiet and disturbed 

 by turns went on in what is now the Helmsdale Oolitic 

 basin; the entire basin from Port Gower to the Ord 

 consisting of successive beds of conglomerate and shale. 

 Should your Grace revisit the locality, it might be well 

 to walk out along the shore to the north-east of Helms- 

 dale for about three quarters of a mile, till you reach a 

 little cottage standing on a point. The shore below 

 consists of a very rough conglomerate bed the upper- 

 most in the basin, and you will have no difficulty in 

 convincing yourself, as you retrace the way backwards 

 through the space laid bare by the ebb, that that bed 

 overlies a bed of shale rich in characteristic fossils of 

 the deposit such as Terebratula, Avicula, Serpula, 

 Belemnites, &c., and which overlies in turn another con- 

 glomerate bed, that overlies yet another shale bed. 

 And thus in regular succession till you reach the river 

 will you find bed succeeding bed the remains and 

 evidence of many periods of tranquillity and of many 

 alternating paroxysms of violence ; and that some of 

 the paroxysms must have been strangely violent indeed, 

 you will find proof in the great size of some of the blocks 

 which the conglomerate contains. Within five minutes' 



VOL. IT. 28 



