BY THE REV. J. E. TENISON-WOODS, F.G.S., tfec. 715 



and which is the type of many other extinct craters in the colony 

 of Victoria. This is the series of lake-craters of Mt. Gambier in 

 the colony of South Australia, forming a piece of enchanting 

 scenery, which has won an almost world-wide reputation. I have 

 already, in my " Geological Observations in South Australia,"* 

 given a description of the blue lake, which is a pei-fectly enclosed 

 basin, about half-a-mile wide, with precipitous sides and a varying 

 depth between 200 and 300 ft. The waters are a dark blue like 

 the open ocean, but they are perfectly pure and limpid, without 

 any excess of solid constituents, unless it be that of lime. 



This is the more extraordinary when we reflect upon it, for 

 usually in lakes that have no outlet, concentration of salts, due to 

 evaporation, gives rise to well-marked chemical characters in the 

 water. The small amount of water does not exactly explain this, 

 because there must be a very considerable quantity in the crater 

 of Taal. No matter what eruptions and changes have taken place, 

 as soon as things get a little settled the lakes are always there in 

 one shape or another. They are always referred to by every 

 historian, though differing in number and shape and sometimes in 

 colour, there has been always a general resemblance, which marks 

 them out as distinctive features of this volcano. They are generally 

 confined to one side of the basin, and usually occupy much the 

 same limits. If they were derived from surface drainage during 

 the rainy season, why are there not waters in all the extinct craters, 

 such as Las Canas 1 But the soil is too porous for rain waters to 

 rest upon it, and there are scarcely any surface accumulations at 

 any part of the island. 



For my own part 1 am inclined to think that these lakes owe their 

 origin to some peculiarity in the emanations of this crater. Vol- 

 canoes vary very much in their products. There are some volcanic 

 centres from which only one kind of lava has been emitted, but 

 there are others in which the changes in the material thrown out 

 are as unceasing as they are unaccountable. Water is always 

 an accompaniment of whatever is emitted from volcanic vents. 

 Water of course in the form of steam. " Along with this steam 



• London, Longmans 1863, 8vo, 404 pp. 



