This is succeeded by a coarse, evenly-grained quartzite, and 

 this by fine-grained arenaceous shales. Two and a half miles 

 N."W. from Ardrossau, on the Kalkabury-road, granite dykes, 

 extending over about two miles, break through, and are accom- 

 panied by chloritic, hornblendic, and micaceous schists and 

 shales, frequently highly indurated. IS^ear the place where 

 the road from Ardrossan to Maitland crosses the Torke 

 Valley Hills, it is not yet exposed in bulk, but only appears in 

 occasional dykes of the " graphic" variety between a highly 

 crystalline "fine-grained gneiss. Similar in occurrence and 

 aspect are all the other granitic areas. 



During the Silurian period some portions of the present 

 land were submerged to very considerable depths, while others, 

 as far as the evidence of the rocks goes, only attained slight 

 depths. The former fact is proved by the fine-grained nature 

 of the respective strata. These limestones — capped and fringed 

 with a thin layer of A^ery hard felspathic conglomerate and 

 sandstone — form the series of rocks which were first determined 

 by Prof. Tate as undoubtedly Silurian from the fossils the 

 middle layers yielded, viz., the dark and variegated Parara 

 limestones mentioned in my former paper. The principal 

 fossils obtained are Strophomena sp., one specimen only ; fairly 

 numerous heads of a Trilobite, apparently eyeless, and varying 

 in dimension from one-eighth to one and a half inch in width. 

 Both these were obtained in the upper layers of a dark grey 

 tint, and are accompanied by numerous impressions of minute 

 molluscs and concretions of ferruginous oxide in the topmost 

 portion. In a detached knoll of flesh-coloured and grey varie- 

 gated limestone, evidently on a lower level, occurs (almost 

 exclusively) a large tabulate coral in great plenty. Prom this 

 knoll the numerous pebbles on the beach, exhibiting sections 

 of the fossil, seem to be derived. Specimens of all these have 

 been submitted to Prof. Tate, who will perhaps favour the 

 Society with a note on the fossils. The " Ardrossan Marbles," 

 considered as the lowest member, appear first in a small dale 

 in Section 7-5, near the road to Maitland, forming the base of 

 the hills as far as Horse Gully, where they are either replaced 

 by the fossiliferous limestones or disappear beneath them, as 

 they cannot be seen anywhere in this deeply eroded gorge. 

 These limestones form well-defined escarpments on both sides, 

 extending some distance inland in nearly horizontal layers, 

 fringed on the west by the marbles, exhibiting the appearance 

 of massive travertines on the surface where weathered (a blow 

 with the hammer, though, reveals their real nature), sometimes 

 enclosing rather sharp-angled fragments of granite or quartzite 

 where, to all appearance, abutting upon them. Their highly 

 crystalline state may therefore be owing to metamorphosis 



