JARVISFIELD MINERAL WATER. 273 



aerial denudation. The late Mr. C. S. Wilkinson, Govern- 

 ment Geologist of New South Wales, estimates the 

 AVianamatta series to be about 700 feet thick ; they consist 

 chiefly of argillaceous shales, and have evidently been formed 

 in the quiet waters of a lake. At Picton valleys of erosion 

 have cut through the entire thickness, exposing the under- 

 lying Hawkesbury sandstones. In a locality near Jarvis- 

 fieki, the residence of Mr, Antill, I have prov^ed the existence 

 of quantities of calcium carbonate in the form of irregular 

 concretions, also in a remarkable deposit known as Cone-in- 

 cone sti'ucture. The underlying Hawkesbury sandstones 

 are freely exposed in the creek beds and other eroded valleys, 

 and they form the natural surface in the vicinity of the 

 spring, A small stream, called the Picton or Stone-quarry 

 Creek, partly encircles the town and empties itself into the 

 Nepean River about two miles to the eastward. Soon after 

 leaving the town the stream traverses a course near some 

 perpendicular cliffs of Hawkesbury sandstone, which show a 

 surface 55 feet high and 70 feet wide ; the top of the cHff" is 

 level with the surface of the ground above. It is from the 

 face of this cliff" that the spring appears. The visitor stands 

 amid the precipitous slopes, which are clothed with ferns, 

 myrtles, and other Australian plants, and sees that from the 

 top of the chff" downwards the rocks look perfectly dry, but 

 from a projecting ledge the water appears oozing out of the 

 horizontal joints and crevices and forms a quick succession 

 of drops coming from a few score of points ; some of the 

 drops fall clear to the foot of the precipice, a distance of 

 about 25 feet, while others fall on to the sandstones and 

 gradually deposit a calcareous encrustation which covers 

 many square yards of the sandstone surface. I have brought 

 a few samples of this calcareous tufa, which often encloses 

 leaves and twigs of the present vegetation ; in some places 

 this tufa is three or four feet thick, and hundreds of tons were 

 blasted off" and burnt for lime some forty years ago. The 

 face of the cliff", and especially the wet part, has somewhat 

 the appearance of the interior of limestone caves when 

 covered with newly formed and wet calcite, but a closer 

 examination proves it to consist of a gelatinous or glairy 

 deposit which yields to the pressure of the hand. I have 

 not had an opportunity as yet of examining this deposit 

 chemically, but it, I believe, requires to be examined biologi- 

 cally, as deposits of the same appearance occur in connection 

 with several of the springs of Europe, especially the thermal 



