Excursion to Mout Park, Bundoora. [v^^' 



Nat. 

 XXXI. 



uncertainly of the weather in the morning iirobahly accounts 

 for the paucity of attendance. Ahghting at Macleod station, 

 on the Ehhani Hne, we made our way u]) the hill through the 

 belt of Golden Wattles to the toji, where a reservoir supplying 

 the adjacent asylum is situated. The object of the excursion 

 was to see the unique dyke cutting through the hill, and to gain 

 an idea of the physiography of the surrounding country. 

 Sugarloaf Hill, as it is known, is a splendid view-point, and is 

 about four miles north of Heidelberg. It is 440 ieet above sea- 

 level, and is an outstanding monadnock or residual hill left by 

 the erosive action on the surrouncUng country by the river 

 system, on account of the comparative hardness of the rock. 

 In all probability this hardness is due to the induration of the 

 sandy shales of the Silurian bed-rock (Melbournian) by the 

 intrusion of the felsitic dyke, and, indeed, fragments of very 

 hard country rock are seen lying about, mixed with pieces of 

 the dyke rock, scattered over the hill, and especially near the 

 excavations made for the reservoir on the summit. The 

 nature of the dyke and the general trend across the hill was 

 noticed. In structure this dyke is a tine-grained felsite. and 

 has burst through the bed-rock across the line of strike. What 

 seems to have subsequently takrn place is the reopening on 

 one side of the dyke, resulting in a mass of fragments torn from 

 the dyke and its brecciated face, including as well sandstone, 

 shale, and milky quartz from the bed-rock itself. I.astly, 

 after a j^eriod of rest, another fault-line was developed midway, 

 and the sides of tlie fissure shaken horizontally, which resulted 

 in giving a " slickensided " or striated enamel face to the adjacent 

 rocks. Specimens of the interesting kinds of rocks were secured, 

 including some nicely jointed masses of sandy clay, in which 

 the structure had probably been produced by the heated 

 intrusive rock forming the dyke. The freshness of the dyke, 

 and the complicated structures shown to be associated with it, 

 make this occurrence one of unicpie interest. One of our 

 members had provided himself with tield-glasses. anfl by its 

 helj) we were enabled to i^ick (ut many distant places of 

 interest along the Plenty Ranges, as well as the distant 

 monadnocks of Kangaroo Ground, and Pine Mont, at Kingwood. 

 The recent removal of the Doncaster Tower was felt to be a 

 decided loss, as it was so useful as a landmark in examining 

 the surrounding country. Finding it would be a rather long 

 wait for the next train at Macleod, we turned our faces to 

 Heidelberg, and caught the 5. 50 train to town, well satisfied 

 with the healthy and enjoyable afternoon's outing, the only 

 regret being that there were so few members participating in 



it.— F. ClIM'M.VN. 



