XXVlll 



Mr. R. M. Johnston, F.L.S., spoke 

 eloquently of the splendid service rendered 

 bv the two gentlemen in the geological and 

 niineralogical interests of the colony. He 

 looked upon the information contained in 

 the paper as calculated to interest geo- 

 logists and other scientists throughout 

 the world. (Applause.) 



FOSSIL CORAL. 



A paper by Mr. Robert Etheridge, jun., 

 Curator of the Australasian Museum, 

 Sydney, ^vas read by the Secretary, 

 Which^ he explained, ^yas descriptive of a 

 Tasmanian species of Halysites. a fossil 

 coral obtained from the River Mersey. 

 Mi\ Stephens presented the Museum a 

 polished specimen of the coral referred 

 to by Mr. Etheridge in his paper. 



Mr. Johnston explained the importance 

 of the paper. 



MACQUARIE HARBOUR : 



Its Physical Aspect and Future 

 Prospects. 



By C. Napier Bell, M.Inst.C.E. 

 In the absence of ]Mr. Napier Bell from 

 the meeting of the Royal Society of Tas- 

 mania on Tuesday evening, Mr. F. Back, 

 A.I.C.E., F.S.S., etc., read Mr. Bell's 

 paper on Macquarie Harbour as follows :— 

 Macquarie Harbour is an immense 

 lagoon of 72,000 acres in extent 

 (a lagoon being defined as a lake Avhich 

 has an entrance into the sea); it is 

 about 25 miles long, and from five 

 to seven miles wide, with several 

 islands in it, and many deep bays and in- 

 lets on its shores. It lies in a S.E. and 

 N.W. direction, nearly parallel to the sea 

 coast, from which it is separated by a 

 tongue of rough, rocky country only a mile 

 or two wide at the entrance, but increas- 

 ing in width towards the south end of the 

 harbour. This tongue of land, separating 

 the harbour from the sea, is, for several 

 miles from Cape Sorell south^yard, com- 

 posed of quartz rock with thick beds of 

 sandstone altered into quartzite, and 

 underneath this quartz is hard slate rock 

 which outcrops on the seashore. Towards 

 the south end of the harbour the land 

 separating it from the sea rises into 

 rough hills of slate covered with bush. 



On the west side of the harbour the land 

 is undulating, and slopes up to the high 

 mountains at the back : it is mostly soft 

 sandstone, shale, gravel, and other sedi- 

 mentary strata, getting more sandy as 

 you approach Strahan, between which 

 and the sea the land is entirely made of 

 white sand, with occasional beds of gravel 

 and peat among it. 



The harbour receives the rivers Gordon 



and King, with a combined watershed of 



. 2,500 square miles, over which the yearly 



rainfall is about lOOin. Very heavy storms 

 of rain are frequent in this countiy, and a 

 downpour of 2.2in. in 21 hours is capable of 

 filling the harbour 4^,ft. above its ordinary 

 levei if this surplus was not emptied into 

 the sea as fast as the rain supplied it. 



A noticeable peculiarity of Macquarie 

 Harbour is its great depth, which is from 

 80ft. to 120ft. all over its area, {.nd even 

 the narrow cove or inlet Avhich forms the 

 harbour at Strahan has over 00ft. of 

 water, while at the south end is Kelly's 

 Basin, a land-locked bay in which the 

 largest man-o'-war could anchor. This 

 peculiarity of great depth of water is found 

 also in most of the rivers of this neigh- 

 bourhood ; thus the Gordon carries a 

 depth of 40ft. to 60ft. for 15 miles from its 

 mouth, although it has a bar of 12ft. where 

 it enters Macquarie Harbour. The 

 King is 30ft. to 40ft. deep for some miles 

 up, though it has a bar of only 2ft. at its 

 entiance with the harbour. But I am told 

 that the Henty and Pieman, ^yhich dis- 

 charge direct into the sea, are also very 

 deep inside their bars. 



I have thought much on this subject, 

 but I have never found a satisfactory ex- 

 planation of the unusual depth of these 

 rivers ; in New Zealand, rivers quite as 

 big and quite as subject to floods are very 

 shallow; the Brisbane River has more than 

 twice the water-shed of the Goi'don, and 

 is visited by tremendous floods, but it is 

 not half as deep ; the Fitzroy River has 

 25 times the water-shed of the Gordon and 

 floods up in places 70ft. high, but it is very 

 shallow in its ordinary condition. 



Speculations as to the origin or mode of 

 formation of a lagoon like Macquarie 

 Harbour are very uncertain in the absence 

 of a thorough knowledge of the geology of 

 the surrounding district. It appears to me 

 that this locality was once a wide, open 

 bay of the sea, bounded on the west 

 by the rockj' hills of the peninsula %yhich 

 ends in Cape Sorell, on the south, east, 

 and north-east by the detached ranges of 

 mountains and their projecting spurs 

 which now lie a long way inland from the 

 harbour, and reach the sea coast near the 

 Pieman River mouth. The gTavel, sand, 

 and mud from the rivers and creeks would 

 then have gradually made the sea coast 

 on the south, east, and north-east sides to 

 encroach on the bay until it began to 

 assume something like its present shape, 

 and then the action of the sea and the 

 currents caused the formation of the great 

 spit or tongue of sand and gravel which, 

 extending from near Strahan, has closed 

 in upon the entrance of Ayhat was then a 

 sound or fiord, and has made it what it 

 now is. a laa:oon, which the sea has no 

 po%yer to entirely close up by reason of the 

 strong currents of the tides which, rushing 

 in and out of the lagoon, keep the mouth 

 always open. 



