322 PROCEEDINGS OF SECTION C. 



below the surface, of waters highly charged with organic 

 matter, — a fact of great moment in accounting for the 

 formation of metallic sulphides and other minerals. 



In order to make clear the circumstances in which this 

 substance is found, it will be necessary to give a brief 

 description of some of the topographical and geological 

 features of the district. To illustrate these the map and 

 section will be useful. The most prominent natural object is 

 a long narrow ridge, known as the " Cabbage-tree Hill," 

 which rises to a height of from 350 to 450 feet above sea 

 level. In this the principal mines are situated. It is com- 

 posed of highly-inclined strata, the succession of which from 

 below upwards is seen in the section, — viz.. Slate, dark 

 graphitic slate, dark grits and conglomerates, lighter grits 

 and conglomerates, dark dense sandstone, light grey and 

 whitish sandstone, bluish dark sandstone, thin-bedded 

 yellowish and whitish sandstones passing upwards into 

 slates, and, finally, a succession of beds of slates, sandstones, 

 and crystalline limestones. Throughout the whole section 

 there is a general dip to the north-east ; but just under the 

 crown of the hill the strata are thrown into several small 

 synclinal and anticlinal folds, as shown. From the eastern 

 base of the hill the ground slopes gently to the Middle Arm 

 of the estuary of the Tamar. Along this base runs a " deep 

 lead " or ancient river channel, which has been determined 

 by the evidence of the fossil flora contained somewhat 

 abundantly in it to be of Early Tertiary Age. The bottom 

 of this old channel has been found by borings and shafts to 

 be some 270 feet below the present level of the sea. The 

 plain between the Cabbage-tree Hill and the Tamar is 

 covered with varying depths of gravels of Tertiary and 

 Recent Age. 



On the south side of the Hill lies an extensive alluvial 

 flat, which most probably is the site of an ancient lake 

 that has partly been filled up and partly drained by the 

 erosion of the gorge of the Middle Arm Creek. Some of 

 this ground has been prospected for gold, and found to be 

 very deep. The former existence of a lake here has probably 

 had a great deal to do with the lignite deposits under discus- 

 sion, as will be seen later on. 



Two main lines of quartz reef traverse the Cabbage-tree 

 Hill, one being that worked in the " Tasmania " mine, the 

 other in the " Amalgamated West Tasmania," " Moonhght," 

 " Olive Branch," and " Little Wonder." It is in the workings 



