750 



ME. C. V. BELLAMY ON" THE 



[Nov. 1900, 



mately the watercourse shown to run from a small backwater to 

 the sea (PL XXXIX, & fig. 2, p. 748). At 12 noon it was found 

 that the surface of the lake was 6*90 feet below that of the sea. 

 Allowing, therefore, for the variation of tide, the conclusion may be 

 drawn that the difference is about 7 feet, and that the deepest part 

 of the lake is probably about 10 feet below mean sea-level. 



(5) Barrier between the Lake and the Sea. 



The nature of the geological formation already described indicates 

 that the lake is divided from the sea by a barrier composed for the 

 most part of shelly sand overlying a bed of stiff calcareous clay, and 

 at intervals along this barrier masses of conglomerates, sometimes 

 hard and sometimes friable, occur : so that the barrier is only 

 porous or permeable in a few places. The appended sketch (fig. 4) 

 may help to illustrate its nature. 



Fig. 4. — Section across the barrier between the salt-lake and the sea. 



a = Permeable strata (sands and conglomerates). 

 b' = Impermeable stratum (clay). 

 b" = Layer of watery matter. 



(6) Results of a Borehole. 



The manner in which these strata overlie each other was ascer- 

 tained by means of a borehole driven on the shores of the lake near 

 the Salt-stores. It was shown by this means that upon the surface 

 was a thin layer of yellowish calcareous or shelly sand about 12 

 or 18 inches thick, then came a thin layer of black mud corre- 

 sponding to the deposit in the bed of the lake. Between the 

 depths of 2 and 10 feet shelly sand again appeared, but intermixed 

 with argillaceous matter, or more strictly calcareous matter in a 

 plastic state, as it consisted largely of carbonate of lime. This was 

 somewhat stiff, and not easy to penetrate ; but between 10 and 12 

 feet below the surface it became very soft, and contained much 

 water distinctly salt. The material brought up by the boring- 

 apparatus was of the nature of ' slurry ' or watery mud. Prom 12 

 to 15 feet of stiff calcareous clay was met with, and beyond this 

 depth the material became so hard as to clog the boring-rods. It 

 was with the greatest difficulty that they could be turned, and 

 they were only withdrawn by pouring water down the tubes to 

 soften the matter. Ten days after the date on which this boring 





