43 



sence of the gravel bed resting between the calcareo-argilla- 

 ceous deposits supports tbe idea that the Gawler Plains not 

 only enjoyed a much moister climate than they now do ; and, 

 also, that their relation to the sea level at the period must 

 have been very different from what it was either before or 

 after the event. (2) The excavation also proves that the 

 aborigines of Australia had at that period entered upon the 

 scene ; and at that early date of their occupancy they had be- 

 come sufficiently knowing to erect a rude circle of stones 

 around the fire so as to retain the heat. 



As further proof of the interstratified condition of the forma- 

 tion in G-awler West, whilst the late Mr. T. Munroe was en- 

 gaged in the excavation of a large tank for the purpose of 

 storing rain-water, after passing through from eight to nine 

 feet of the semi-clayey deposits characteristic of the subsoils 

 of Gawler Plains, a bed of gravel was struck, which impressed 

 me forcibly at the time of its having been caused by river 

 action, and, if so, it is evident that the channel of the South 

 Para — a little to the west of its outlet from the hills — then 

 flowed over the plain rather more than 200 yards to the south 

 of its present course ; and that its channel was then about SO- 

 feet higher than the level of the bed of the present stream. 

 Similar illustrations may be found in sections given in various 

 papers published by the Eoyal Society of this colony. 



Probahle Date of the Last Glacial Ej^ocJi. — At the time when 

 I penned my brief sketch of the "Geology of Munno Para" I 

 was under the impression that the last extreme glaciation of 

 the southern hemisphere in point of time had preceded the 

 epoch in the northern hemisphere known as the glacial, and its- 

 intensity had begun either about 980,000 years since or about 

 720,000 years ago. But after reconsidering the subject more 

 carefully I arrived at the conclusion that it must have been in 

 connection with the last term of high eccentricity that a 

 glaciation of the southern hemisphere occurred, which, accord- 

 ing to Dr. Croll, took place between 240,000 and 80,000 years 

 ago. At that period a high state of eccentricity continued for 

 a term of 160,000 years, which according to the laws governing 

 the precession of the equinoxes, each hemisphere would pass- 

 through during that term about eight periods of extremes in 

 cold and heat. The diversiform character of the summers and 

 winters which then must have prevailed would lead to a much 

 greater rainfall than is now witnessed over the Australian 

 continent, and which would continue in a state of greater or 

 lesser intensity for about 10,000 years respectively. 



A Glacial JEpoch at the Close of the Pliocene Period. — ■ 

 Scanty but indubitable relics are left to show that the 

 continent of Australia was affected b3^ cosmical changes 



