96 Proceedings of the Royal Society of Victoria. 



the stone composing this part of the core, whicli has the 

 appearance of having been crystallised out of a saturated 

 solution of mineral salts. Beds of gj'psum and rock-salt 

 formed in this way are common, but massive calcite so 

 formed is rare, as far as I can ascertain. This is probably 

 owing to the great solubility of bicarbonate of lime. Calcite 

 is formed in two ways : — (1) In lakes which are drying up, 

 the carbonate of lime being supplied to it by the streams 

 which feed it. Evaporation of its waters tends to concen- 

 trate the salts, which are then deposited in crystals on its 

 floor. (2) In nearly closed arms of the sea, such as the 

 Adriatic, which is fed by numerous streams, which cut their 

 courses through calcareous or volcanic rocks. The fresh 

 water being the lighter, spreads out as a thin sheet over the 

 salt water, and is in this way exposed to the evaporating 

 influences of sun and wind, whereby it becomes a concentrated 

 solution, and so deposits its salts as crj^stals. 



The floor of the Adriatic is now being formed of calcite, 

 and this is the explanation given of it by the text books ; 

 but I confess that I feel a difficulty in accepting the state- 

 ment, that there can be sufficient concentration of the waters 

 in the open sea to deposit carbonate of lime. 



There is another explanation offered, which is that in the 

 presence of sodium carbonate, lime salts are decomposed, and 

 then calcite is precipitated. 



The stratum of calcite in the bore at Warrnambool may 

 have been accumulated in one of these ways. It may represent 

 the bottom of such a lake as those which edge the Ninety 

 Mile Beach in Gippsland, or it might have been deposited in 

 the sea ; but it seems to me that in the latter case, that sea 

 must have been a partly closed one like the Adriatic, rather 

 than an open strait like Bass' Strait, in which any sufficient 

 degree of concentration of its waters would hardl}^ be possible. 

 Or again like the Rhone, which has at its mouth a deposit 

 of calcite, the Hopkins which has a course which cuts across 

 volcanic rock and limestone beds, may have poured into this 

 arm of the sea a large volume of water charged with bicar- 

 bonate of lime which, coming into contact with carbonate 

 of sodium in the sea water, is reacted upon and precipitated. 



Bed No. 8. Light Yellow Marl, 2G ft. G in'. Teiick. 



Marl is generally a lacustrine deposit, and is then composed 

 of the mouldered shells of mollusca, and the remains of algse. 



