THE VICTORIAN NATURALIST. 21 



EXCURSION TO KEILOR. 

 This excursion was timed to leave Spencer-street by the 12.15 

 train on Saturday, 8th April, but at the appointed hour only three 

 members put in an appearance. The day was a beautiful one, 

 on which a fair attendance might have been reasonably expected. 

 However, nobody else appearing, the three set out, and after a 

 twelve miles run found themselves at St. Albans, a solitary hamlet 

 on the Keilor Plains. From here we walked in a north-easterly 

 direction to a tributary creek of the Saltwater River, noting the 

 vesicular and slaggy appearance of the basalt in many places. 

 Owing to the columnar structure and ball and socket joints of the 

 basalt the ground is often strewed with loose masses of rock. The 

 creek, which does not appear to be named, is crossed by a road 

 to Keilor a short distance above its junction with the Saltwater 

 River. The valley is typical of the many similar ones that traverse 

 these plains, being about 250 ft. or 300 ft. deep. Walking along 

 the right side of the valley, before coming to the road mentioned, 

 we noted an outcrop of a yellow, earthy limestone, capped by grit 

 and a very hard white quartzite. This limestone, which was the 

 object of our visit, is traversed by numerous veins of limonite, 

 which very often assumes a concretionary form. On examining 

 this limestone more closely we found it to contain a quantity of 

 Polyzoa and Echini spines. Some imperfect casts of Lamelli- 

 branchs were also observed. This deposit has been put down as 

 of Pliocene age. A little further on we came to a section exposed 

 on the side of the road close to the bridge across the creek. The 

 succession here, beginning at the bottom, is first basalt, much 

 jointed and much decomposed. This is overlaid by the Pliocene 

 deposit before mentioned, and this again by the basalt forming 

 the surface of Keilor Plains. The lower basalt is what is known 

 as " Older Volcanic," and up till recently has been considered as 

 probably of Miocene age. However, Mr. G. B. Pritchard has 

 lately shown that a basalt occurs at Portarlington which is over- 

 laid by deposits of undoubted Eocene age ; so it is quite possible, 

 even probable, that the basalt we are considering is older than 

 Miocene. In the sedimentary deposit overlying this the gradual 

 change from a quartzitic grit to a fine-grained, almost crystalline 

 quartzite can be well seen, the change having been probably 

 brought about by the overlying basalt when it poured in molten 

 floods over the country. This upper basalt — Newer Volcanic, as 

 it is called — has been set down as of Pliocene age, and Murray 

 discusses the probability of its having been spread out under 

 water. This seems to have been the case in some instances, at 

 any rate. I am inclined to think that this Upper Volcanic series 

 will have to be placed further back in geological time. On 

 examining the old cones of eruption about Sunbury and Diggers' 

 Rest one is surprised to find how little of their original structure is 



