790 GEOGRAPHY OF BLUE MTS. AND SYDNEY DISTRICT, 



basal conglomerates unconformably overlying finer beds. Other 

 conglomerate and grit beds occur higher up in the series, though 

 subordinate in importance to the great basal examples. Alter- 

 nating coarse and tine-grained measures, and also bedded and 

 lenticular limestones, occur in the inter-conglomerate spaces. 

 The basal layers of boulders and pebbles argue a pronounced 

 epeirogenic movement accompanied by folding which closed one 

 series of cycles while inaugurating another. During the early 

 stages of the initiatory cycle the torrential action (owing to 

 increased stream grade) of the new streams resulted in great loss 

 of boulders and pebbles along the shore, while the succeeding 

 finer-grained masses evidence the pronounced subjugation of the 

 continuous mountain system. The alternation of coarse and fine 

 layers in vertical succession points to oscillations of movement — 

 here a layer of grit indicating elevation, there a coarse-grained 

 and cross-bedded sandstone evidencing rapid stream-movement, 

 a bed of sandstone or lens of limestone illustrating calm con- 

 ditions. The occurrence of conglomerates overlying fine sediment 

 or growth as coal seams or mudstones implies the rejuvenescence 

 of elevation succeeding pronounced erosion or slow subsidence 

 and concomitant sedimentation; if the conglomerates be im- 

 portant, a new cycle is demonstrated. Xor must we lose sight 

 of differential and accentuated movements. After elevation, 

 subsidence oscillations act in the direction of diminished erosion 

 and consequently finer sedimentation. A rapid rise after youth- 

 ful sinking minimises the etfect of the drowning. Thus from a 

 consideration of such a system as the Permo-Carhoniferous the 

 existence of numerous large and small cycles is proved. Each 

 vibration of movement resulting in a layer of sand or mudstones 

 is overshadowed by the epicycle, each epicycle with its grits, &c., 

 is dominated by the cycle, which in turn expresses but a fraction 

 of the period. 



I desire here to thank Messrs. Dun, Morrison, and Murton for 

 assistance and information supplied in the preparation of this 

 work. 



