QROLOOY OF 'mii AVON BASIN. 



lied, wliile I have detected a few fragments of the Bryozoa 

 Bed of the Lower Limestone Shales. It is difficult to under- 

 .stand how this deposit, containing so largo and such mixed 

 fragments, angular or but little rounded, and many of them 

 from some little distance, embedded moreover in a matrix 

 which also contains smaller also snb-angulai' fragments, could 

 have boon formcnl except by the .agency of ico. 



Tho hill is entii-ely composed of Dolomitio Conglomer.ato ; 

 .and it is unfortunate that on Mi'. Sanders' map tho name 

 Gonygar Hill is printed, not on the hill itself, but on tho 

 Old Hod Sandstone which lies to the S. The whole of this 

 irregular ridge, of which this hill forms a fragment separated 

 by the notches cut by tho Portbury aiid Charlton brooks, 

 is oompos(!(l of this resisting rock, a belt of softer low-lying 

 Triassic Marls forming a band between this rock and the 

 alluvium of tho fl.ats. 



The open country S. of Conygar Hill is composed of soft 

 sandy beds of Old lied Sandstone, the loose and friable 

 nature of which is well seen at the points marked a and h on 

 tlic map. The upper beds of Old Red Sandstone, the out- 

 cro|i of wliicli is farther ISf., are, in fact, conglomeratic, and 

 lor the most pai't harder and of greater resisting power. It 

 is those upper bods which give rise to the ridge through 

 which the Portbury brook cuts the wooded combe to the 

 W. of Windmill Hill. Tho line of depression to the K. of 

 this ridgo marks the outcrop of the Lower Limestone Shales, 

 but the now dry tributary which once flowed through Lower 

 Combe, cut across tho Old lied Sandstone, as sliowu by tho 

 dotted lines on the map. 



Lot mo here turn aside for a paragraph to note n, matter 

 or detail, but one of sonio little importance. 



The student of our local geology should not fail to mako 

 liimsolf acquainted with one of the most chai-acteristic beils 



