XV 



plains, with maximum depths of 16, 12, 

 and 18ft. respectively; and the Middle 

 Reach, north of South I>ake, is shallower 

 still; in the second place, the water en- 

 tirely round the vast outline of the lake is 

 so low that, at the time of our visit, the 

 boat could in very few places be brought 

 less than 30 yards from the shore. The 

 water was, it'^ is right to mention, 2ft. be- 

 low normal level. At one spot, it was 

 not a foot deep 6O0 yards from the shore, 

 and in other ple.ces we had to wade 150 

 yards so as to land. The effect, there- 

 fore, of a heavy drain on the lake would 

 be serious with a fla,t shore of this kind. 

 We conclude with a few remarks on the 

 practicability of using the lake as a reser- 

 voir. 



The above-mentioned dfata and calcula- 

 tions will serve to show to what extent the 

 lake acts as a reservoir, turning an inter- 

 mittent supply into a constant stream. 



During the night referred to above, on 

 which we were camped at Kermode's 

 Neck, over two inches of rain fell in a few 

 hours at the north end of the lake, bring- 

 ing the five principal creeks flowing into 

 thet end to a state of high flood. Twenty- 

 four hours after the flood was at .'ts 

 height, the flow of the creeks was gauged; 

 the flood marks would be seen far above 

 the banks, but the creeks, though full, 

 were within their banks. 



It must be mentioned here that one 

 ':reek had been gauged before the rain 

 fell, viz., Kimberley Creek, and there the 

 flow after the rain was fount to be ten 

 times what it was before; the total inflow 

 of all the creeks was about 100 times the 

 inflow of the Hobart water supply at th.p> 

 Gentle Annie falls, just above the reser- 

 voir. In a very few days, doubtless the 

 creeks would go back to the previous con- 

 dition of discharging one-tenth that 

 amount. Then another storm would come 

 along, and another flood. 



Let us consider how the outflow from 

 the Gretat Lake would be affected by this 

 intermittent supply. In the first place, 

 we have the evidence of the Meteorologiial 

 Observer at the south end of the lake 

 that this flood at the north end produced 

 no perceptible difference in the Shannon; 

 we, ourselves, gauged the Shannon when 

 we arrived there four days after the rain, 

 and found the outflow from the Great 

 Lake to be at the Pate of 13,000, OOOgai. 

 for 24: hours. 



What then had become of the flood at 

 the north end? A little calculation will 

 serve to show : The area of the Great Lake 

 is approximately 28,400 acres; 300,000,000 

 gal. spread over this area would approxi- 

 mately amount to a third of an inch in 

 depth. 



From this it is apparent that the great 

 extent of the lake is quite sufficient to ac- 

 count for the equalisation of the flow of 

 the Shannon, and its apparent indiffer- 

 ence to an occasional flood. 



Colooel Legge forwarded the follow- 

 ing additional note : — 



Please express my regret to His Excel- 

 lency that I am not present to-night to 

 take part in the discussion on the paper 

 cead last meeting on the Gre^it Lake. I 

 trust our investigations will at last throw 

 some light on the vexed question of the 

 supply of water to the Great Lake. Al- 

 though theve is, doubtless, a very heavy 

 discharge through the Shannoti in the 

 winter from the lake, there is compara- 

 tively little when the water is at summesr 

 level, as our investigations show 

 203,000,000 gallons flowing in during 

 rain, and 13 million flowing out under 

 like conditions, for 24 hours. There- 

 fore. iiQ oonneotion with the use of tihe 

 lake as a reservoir the cjuestion to be 

 consider'ed is loss of water in the sum- 

 mee- by evaporation and absorption. The 

 suns rays are powerful in the rarified at^ 

 mosphere of the la.ke, and the ^oss of 

 water from these latter causes is forgot- 

 ten, more than that by overflow. This is 

 proved by Mr. Buckley, C.S.I. , in tis 

 interesting paper on the East African 

 Protectorate to be a very importa>nt fac- 

 tor in the case of Lake Victoria Xyanza. 

 Tlie maximum discharge from it Ijt the 

 Xile, over the Papon Falls, is shown to 

 be 30,000 cubic feet a second, which only 

 lowers the lake level about li inch in 

 a month. On the other hand the re- 

 duction in the lake levels is at times so 

 considerable, as shown by the '^greoges,"' 

 that afterr deducting tfoe loss for over- 

 flow at the above amount, it leave's a 

 balaoce of 7 or 8 inches a month to tbe 

 effect of evaporation. This astonishing 

 difference is due to the tropical sun, in 

 spite of the large area of the lake, which 

 is more than 2,000 sc^uare miles larger 

 than Tasmania , but these results must 

 convince one tliat even in the lesser de- 

 gree, due to climate and small size of the 

 Great Lake, the loss in summeir by evaj)- 

 oration is very co»nsiderable. It would 

 not be difffcuit to estimate it, if gauges 

 were fixed up by the Government at the 

 Lake. The results would be more inter- 

 esting to students of the Physical Geo- 

 granhy of Tasmania, if to no one else. 



Mr. Kingsmill, in opening the discus- 

 sion, said they bad been told there was 

 a great hole somewhere in the Great 



