Xll 



ABSTRACT OF PROCEEDINGS, AUGUST, 1903. 



INTEEESTIXG PAPERS. 



At the moiilfhly meeting of the Royal 

 Society of Tasmania on Tuesday evening, 

 August 11, His E^xcellency the Governor 

 (Sir Arrhur Havelock) presided. 



COXTS-IBUTIONS TO THE PHYSIO- 



GEAPHY OF TASMANIA. 



No. 2. 



RAINFALL AND WATER SUPPLY OF 

 THE GREAT LAKE. 



(By Mr. H. C. Kingsmill and Colonel 

 Legge, R.A.). 



In March last, a trip for scientific pur- 

 poses was made b3' us to the Great Lake, 

 C'.nd, as part of the work, we undertook 

 the investigation of the supply of water 

 Ho wing into the lake at the north, and 

 mountainous, end. As is well known, the 

 character of the country at the north is 

 totally different from that at the south : 

 the bare plains and barren hills of the 

 latter giving wi^iy to the bold ranges of 

 rocky mountains and glades and valleys 

 of damp, boggy soil, which constitute the 

 reverse slopes of the Great Western Moun- 

 tains. 



We were induced to pay attention to 

 this subject owing to the wide-spread idea 

 that the Great Lake has no "feeders," 

 o.nd that the outflow through the Shan- 

 non at th3 south end is compensated i u* 

 by the influence of springs at the bot- 

 tom of the lake. We would here remark 

 that, from the results of our numerous 

 soundings all over the lake, no bottom is 

 more unlikely to contain springs. 



As the result of a previous visit by one 

 of the writers to the lake, a meteorological 

 station was established tat the north end, 

 under the care of Police Trooper Archer. 

 (Observations commenced at the Little 

 Lake in June, 1902. In that we now have 

 a year's record, revealing one of the most 

 interesting cases of great variation in rain- 

 iVail between two contiguous stations that 

 can probably be found in Tasmania. 



As "the crow flies," the distance be- 

 tween the south end of the lake — 'Swan 

 Bay— and the Little Lake at the north end 

 is about 15 miles. At the former the rain- 

 fall was 18.0 inches during the 12 months 

 ending May 31, and has averaged 33.87 

 inches during the past years; while our 

 record at the station on Little Lake for 



the same period — June 1, 1902, to May 31, 

 1903— reaches a total of 63.62 inches. 



This remarkable difference in the fii.. 

 at the two ple.ces is caused by the prox- 

 imity at the north end of the lake to the 

 high mountains of the Western Eanges, 

 which catch all the rain coming from che 

 west and north-west, and precipitate it 

 on the watershed bet«-een Dry's Bluff, 

 with its contiguous mountaiusi and the 

 lake shores. Although this watershed is 

 one of inconsiderable depth, measuring 

 from north to south, it is traversed by 

 several not unimportant streams, which 

 lead to the lake in a belt of only about 

 four miles in width. 



After a heavy nighty's rain, with a fall 

 of two inches, which is of frequent occur- 

 rence, these streams come down in high 

 flood, which, from observations we made, 

 kists two or three days, and pours an im- 

 mense body of water into the lake. This 

 es especially the case as regards the prin.- 

 cipal "feeder"" — omitted for some unex- 

 plained reason from the maps — and which 

 we are desirous of naming the "Shannon. 

 Rivulet," as it may be considered as much 

 o. part of the Shannon as the upper por- 

 tions of the Shannon River in Ireland, be- 

 fore it flow? through the splendid lakes 

 which are renowned for their salmon fish- 

 ing. The rivulet in question rises in a 

 locality ce.Ued by shepherds, "Half Moo.'i 

 Marsh Creek," little above the Pine Lake 

 on the crest of the Great Western Moun- 

 tains, and flovfs through the Half-Moon 

 Marshes, and into the Little Le.ke, which 

 empties by what is known as the "chan- 

 nel" into the Great Lake. 



As illustrating the effect of one of the 

 heavy downpours which are frequent at 

 the north end, while there is scarcely any 

 rain at the south, we may mention that 

 on the night of Mo.rch 2, we were camped 

 at the Little Neck, which is half-way 

 down the lake. It commenced to rain 

 about 11 o'clock, the fall being by no 

 means heavy — a steady rain, with mode- 

 rate breeze from the north — and continu- 

 ed till 9 a.m. next morning. At this time 

 a strong north-west wind was blowiTjg, 

 against which we had to pull in a heavy 

 sea most of the day before we could get 

 into position to sail home. On our arrival 

 at the north end, Ave were met by the dark, 

 peaty waters of the flood from the Pine 

 Lake, about three-quarters of a mile from 

 the shore, and reached our landing place 

 in the channel with much difficulty. We 

 found that there had been heavy down- 

 pours of driving rain, commencing earlier 

 than with us, and continuing without in- 

 termission till 11 a.m. the next morning, 

 the fall registering by 9 a.m. inches. 



At the Little Neck, 10 miles south, we 



