THE VICTORIAN NATURALIST. ^ 41 



The Silurian to the east of the Granite, as well as the eastern 

 boundary of the latter, is shown on the Geological Survey 

 Quarter Sheet Map No. 12, N.E. (Bacchus Marsh), and the 

 sections accompanying the map show the folding of the Silurian 

 and clearly indicate the intrusive nature of the Granite. 



However, in working out the sections given herewith I have 

 obtained somewhat different results from those given by the 

 Geological Survey. At the time of the survey the sections were 

 clothed with a dense scrub woven together by various climbing 

 plants. This, together with the surface soil, has, owing to the intro- 

 duction of rabbits, been almost entirely removed ; however, I 

 find the map accurate in boundaries, position, and direction of 

 watercourses, hill shading, &c., and greatly regret that the 

 country to the west is beyond the pale of the survey. 



Starting from the first exposed section of Silurian on the 

 Werribee River about 5^/^ miles west from Bacchus Marsh, and 

 following the river and gully beds beautiful sections are seen ; they 

 vary in height from a few to over 500 feet, and are composed of 

 clay, slate, quartzite, quartzose, and sandstone bands all highly 

 inclined, the dip ranging from 30° to 90°, the average being about 

 70°. Generally speaking the dip to the west is higher by 10° to 

 20°. Several anticlines have been observed in which the dip to 

 the west is from 40° to 50° greater than the eastern leg. Current 

 bedding, or, rather, a rapid thinning out of sandstone and other 

 beds, and probably ripple marks, have been observed. Anticlines 

 and synclines follow in fairly rapid succession, on an average 

 six to the mile. 



Following the axes of the folds to the south, some are observed 

 to gradually die away, while others become more strongly 

 developed, and fresh folds appear. Mr. T. S. Hall, M.A., has 

 recorded a similar feature in a paper read before the Royal 

 Society of Victoria, loth May, 1894, entitled "The Geology of 

 Castlemaine, with a Subdivision of Part of the Lower Silurian 

 Rocks of Victoria and a List of Minerals." The pitch of the 

 anticlines is fairly steep, being between 8° and I5^ Several 

 have, however, been observed with the pitch as high as 60°. 

 When seen in section, with the pitch towards the observer, they 

 are somewhat difficult to make out. Generally speaking local 

 movement has been detected in the immediate neighbourhood of 

 anticlines with an abnormal pitch. 



Faulting has not been detected to any great extent. One of 

 about 40 feet, and many others of less amount, have been observed. 

 In cross-faulting the movement has been from west to east ; several 

 beautiful examples of slight faulting are to be seen in the cuttings 

 on the Ballarat and Melbourne railway line. 



Cleavage is developed in certain portions of the Silurians, 

 almost if not quite obliterating the bedding planes, generally 



