194 NOTES ON SOME GEOLOGICAL OBSEBVATIONS, WEST COAST. 



seems likely, Macquarie Harbour once had a wide mouth 

 instead of a narrow one, and the sand driven southward "by 

 the north-westerly winds has gradually formed a sandspit 

 from Strahan to the Heads, it seems likely that the dunes 

 represent successive lines of sandhills formed above high 

 water mark, and that the land has been reclaimed by the 

 constant deposit of sand brought in to the shore by the 

 action of the winds and waves. The reclamation would be 

 similar to that which often takes place in the angle where a 

 breakwater meets the shore line on the side exposed to the 

 prevailing winds and currents. In this case Cape Sorell and 

 the strong current from the Harbour would be the obstacles 

 preventing the further southward travel of the sand, and 

 causing it to accumulate on the beach to the northward. If 

 this suggestion is correct, the depth of the deposit of sand is 

 probably considerable, much more so than if the dunes were 

 formed by the action of wind alone. Perhaps some of the 

 railway cuttings may throw some light on the question. It is 

 interesting from an engineering as well as from a geological 

 point of view, and has a certain bearing upon the proposed 

 harbour works at Macquarie Heads. From its geological 

 aspect, a section through such a sand deposit as I have 

 indicated would exhibit an instructive succession and overlap 

 of horizontally bedded sands, false bedded sands, and blown 

 sands. 



The gravel deposits in the neighbourhood of the Pieman 

 Eiver and along the road from Corinna to Long Plains 

 deserve some attention. They cover a large extent of 

 country, and are found at very various levels, and they 

 appear to have been laid down when the river systems were 

 not altogether as they now are. As gold has been found 

 almost universally in these gravels, though in small quantity, 

 they may become of economical importance, and leads may 

 be found in them. Their distribution and formation are 

 therefore worthy of study. 



An alluvial deposit at the Linda Eiver, in the neighbour- 

 hood of Mount Lyell, where sluicing operations for gold are 

 being carried on, also came under my notice. The streams 

 that piled up the auriferous gravels were probably much 

 larger than those now existing. Under the gravel there is a 

 peaty bottom, containing very numerous fragments of wood, 

 apparently of one of the pine family. Below this bottom 

 another layer of gravel has been found in places. Search 

 would probably reveal leaf beds, from which valuable 

 information might be obtained. The alluvial flat through 

 which the Linda Company's tail-race runs, may very probably 

 have been at first a small lake, then gradually filled up to a 

 marsh, and finally covered over with a layer of gravel. If so, 

 what force scooped out the Lake basin ? Was it a glacier, 



