292 PROCEEDINGS OF SECTION C. 



The principal portion of the Bowning Beds is that lying 

 between the eastern boundary and the porphyry ridge about a 

 mile west of the town, and forming a synclinal basin. Here the 

 sedimentary rocks have escaped in a remarkable manner the work 

 of metamorphism. In the eastern half of the basin this escape 

 is particularly remarkable, while in the western half the excep- 

 tions consist in the silicitication of some of the original strata 

 over certain areas. The general strike is nearly north and south, 

 and the dip east and west in the syncline, and the dip for the 

 whole area north of west ; and in the syncline ranges from 

 0° to 90°. 



The basin is ti-aversed by numerous small creeks, many of which 

 cut the beds at nearly right angles to the strike, and all more or 

 less expose the strata. The Great Southern Line crosses them in 

 a similar direction and exposes good sections in many places. 



Sequence of the Beds. — That ternary arrangement of deposition, 

 which has been shown by the late Professor Phillips, Dr. Geikie. and 

 other eminent geologists, to have taken place in the formation of the 

 sedimentary rocks of Palaeozoic times in Britain and elsewhei^e is 

 also a marked feature of the Bowning Beds, though it does not 

 repeat itself here with such marked and regular persistency, as it 

 is shown to do in some of the localities cited by the authorities 

 mentioned above. 



In the lower beds the succession of the ternary order is clearly 

 defined. For on the east at Silverdale, where they are well exposed, 

 grit, shale, and limestone may be seen repeating themselves rather 

 frequently. The bed that I shall refer to in the course of this 

 paper as the Lower Limestone bed, is, in reality, composed of a 

 number of thin strata of grit, shale, and coralline limestone, 

 succeeding each other with tolerable regularity. In each case at 

 this stage the strata are thin, ranging from an inch or two, to as 

 many feet, the shale and grit usually being thinnest. These 

 succeeding changes of sedimentary deposits indicate that our 

 Silurian sea floor, like those of the same age in other quarters of 

 the globe, was subject to frequent change of level. 



Above this cycle of beds a considerable bed of grit occurs, 

 followed by the principal bed of limestone, which in turn is covered 

 by the Lower Trilobite Shale bed, affording the last and most 

 striking example of this particular order of sedimentation to be 

 found in the series. 



Among the upper beds the limestone is absent ; but still a 

 ternary order is maintained by shales, grits or sandstones, and 

 conglomerates. 



On the eastern side of the syncline the order of the beds is as 

 follows : — Grit and shale followed by the Coralline Limestone 

 which, as above pointed out, is interbedded with grits and shales, 

 then succeeds the grit separating the two limestones, and next the 

 thiL^' bed of limestone, in the structure of which Favosite corals 



