203 



equivalent number of feet. This is, of course, due to the fact 

 that the ground water is only filling crevices, pore spaces, 

 and occasional rifts and caverns in the limestone rocks. In 

 some cases, as in the dry year of 1902, or the wet year of 

 1906, the effect on the level of the lakes was not proportionate 

 to the rainfall. It is suggested that this is due to the varia- 

 tion in the amount of water that percolated into the ground, 

 dependent on the distribution of such rainfall throughout the 

 years mentioned. In 1902, for instance, the proportion of 

 water that soaked into the ground may have been relatively 

 greater than that of the wetter year of 1906. 



In drawing the various curves it was found that those 

 based on the rainfall of County Low an bear the closest 

 resemblance to that of the variation in the Mount Gambier 

 lake levels. It seems fair to accept this as corroborative 

 evidence of the opinion that a considerable portion of the 

 underground water conies from the Lowan area. There must, 

 however, be a fair percentage of percolation into these lime- 

 stone beds from the general rainfall of the Mount Gambier 

 district, so that the variation in lake levels is dependent on 

 both factors. The curve D (fig. 11) is drawn to express this, 

 being: based on the mean of the two sets of annual rainfall 

 figures given above. 



From the evidence given in these graphs one would be 

 fairly safe in prophesying the movement of the water level 

 in the lakes, year by year. According as the year's rainfall, 

 up to say October or November, varies from the average of 

 18 to 20 in., there would be an appreciable rise or fall in the 

 December level, from that of the previous December, by an 

 amount that could be calculated (approximately) from the 

 graphs given in fig. 11. 



10. Scenic and Economic Aspects. 

 Though the geological features of the Mount Gambier 

 volcanoes are on so small a scale, they have had a very great 

 influence from the economic point of view. 



The fertile soils of the ash deposits, together with the 

 visible unlimited water supply of the lakes, led to early settle- 

 ment in the district, and to the rise there of a well-built and 

 prosperous town, that has become the chief centre of the 

 south-eastern districts of South Australia. 



The history of the volcanic area having been so unusual 

 and varied, as herein imperfectly described, the resulting 

 scenery is equally notable for its variety, beauty, and un- 

 expectedness. For this reason the town has become noted as 

 a tourist resort. Practically the whole area of the Mount 



