48 Excursiofi to Essendon. [^^'^juiy^^'^' 



EXCURSION TO ESSENDON. 



Favoured by a fine autumn afternoon, about thirty members of 

 the Club and half a dozen students from the Continuation School 

 Geology Class assembled for this excursion on Saturday, 14th 

 May. The outing had been arranged for the purpose of studying 

 the geological and physiographical features of the country lying 

 to the vvest of the railway, towards the Saltwater River, and the 

 well-known "Horseshoe Bend," nearly two miles from the station, 

 was made our objective. Proceeding westerly along Buckley- 

 street, attention was drawn to the sandy nature of the surface 

 soil, indicating probably that the underlying rocks are portions of 

 the marine or estuarine Tertiary sandstones of southern Victoria. 

 Descending into a broad, shallow valley, trending in a southerly 

 direction towards the Saltwater River, some of the reasons for its 

 shape were pointed out, and its form contrasted with the gorge- 

 like characters of the younger valleys at present being carved out 

 in country covered by tiie Newer Volcanic lava flows. As we 

 proceeded the country became almost level in character, with 

 here and there slight undulations. A little to our left was a 

 wide, slight eminence capped with a thin mask of extremely 

 vesicular basalt of the " bread-crust " type, the first outlier of the 

 main area of the Newer Volcanic lavas of the Keilor Plains. Just 

 near the wooden post marked " E, T. B.," which indicates the 

 boundary between Essendon city and Keilor shire, a slight road- 

 cutting revealed a splendid series of stages in the weathering of 

 the older basalt, which underlies the Tertiary sandstone of the 

 district. In parts the basalt is weathered into the softest of 

 wackenitic clays, which are white, creamy, yellowish, brown, pink, 

 red, and black, according to the character of the iron salts stain- 

 ing them. A small creek crossing the road served to provide 

 material for remarks on the erosive action of water. Here we saw 

 how surveyors' marks, cut during the *Mand boom/' seventeen or 

 eighteen years ago, had become miniature runnels in time of rain, 

 and, leading to the creek in question, it in turn had been 

 deepening and widening its channel, so that it — a rejuvenated 

 stream — bore all the characters of a canyon on a small scale. A 

 short, sharp climb now brought us on to the highest elevation 

 attained during the afternoon, the top of the eastern edge of the 

 Keilor lava plains, which have replaced what must have been 

 anterior to their formation an eroded land surface with its ridges 

 and valleys. These have been covered up and a new drainage 

 system superimposed on the country. At this point, just north 

 of the Horseshoe Bend, numbers of quartzite and porcellanite chips 

 and flakes of artificial origin, evidently left by the aborigines who 

 formerly wandered over these parts, were picked up. A minute's 

 walk southward brought the party suddenly in full view of the 

 Horseshoe Bend of the Saltwater River. From a height of about 

 145 feet above sea level the Saltwater River could be seen 140 



