BY SYDNEY B. J. SKERTCHLY. XXV 



the lines of least resistance, that is along the joints, and so are 

 formed bedded lodes, Class V. If the plates craak, faults are 

 formed and an easier outlet produced, and so we get impregna- 

 tions from faults, Class IV, evidently richer than Class V. If 

 the boiler breaks or splits we have trua fissures. Class I., through 

 which and along which the steam will pass and condense : clearly 

 they are richer than any of the other classes. If the boiler were 

 lined with a more or less plastic substance this would be forced 

 through the fissures and steam with it, and so we get Class II, 

 the dyke lodes. 



Finally we have Class III, the Carbonas, to account for. 

 Let our boiler cool down after large cj^uantities of the plastic 

 inner material had been extruded. It is plain that along the 

 junctions of the extended masses with the plates we have lines 

 of weakness, and if the boiler be again heated, the steam will 

 most readily escape along the sides of the old rents. This is pre. 

 cisely what has happened ; the extruded plastic matter is the 

 granite, etc., and here we have the clear explanation of the law 

 laid down above, that the carbonas are on or close to tlie junc- 

 tion of the igneous and sedimentary rocks. 



One other point deserves notice, the ironstone outcrops. 

 The ironstone is in the form of limonite, h;ematite, or magnetite, 

 and as the old German adage has it : — 



" Happy is the lode that wears an iron cap." 

 There are, however, unfortunately for prospectors, two sets of 

 ironstone, the one \aluable, the other valueless, and they are 

 mineralogically the same. The ironstone which is valuable as 

 an indication of lodes has come from beloAV as described ; the 

 worthless ironstone is simply the residuum of the iron suffused 

 through the limestone, carried down by rain-water and deposited 

 at its base. It often forms really good haematite, but of no 

 thickness, and where the limestone has been denuded away and 

 left the ironstone outstanding, only a knowledge of the geological 

 features can discriminate between this and the true lodestuft". 



('(>)iclH(li)t(/ llciiKiii.s. — Having thus sketched, though in 

 meagre outline, the chief geographical and geological features of 

 this remarkable district, a few words may appropriately be de- 

 voted to the question of its future. If wisdom is born of experi- 



