Thames, North Island of New Zealand.

This gold-field, in the Coromandel Peninsula of the North Island, presents a new type of country-rock, as compared with those considered above, all of which (except that of Charters page 20 cially as the solvent action of water percolating through sedimentary rocks during their metamorphosis would almost certainly be greater than that of the water which carried silica in solution and formed the quartz-reefs. The detection of gold in these quartz-folia, at a long distance from any auriferous lode, would therefore give strong support in this case to the lateral-secretion theory, and vice versa.

Table XII. contains the results of analyses of such quartz-folia from the Tipperary deep adit, together with a few similar samples from the Premier mine. It shows that the quartz-folia in this mica-schist are not auriferous when sulphides are not present, and that sulphides are present in appreciable quantity only when the quartz-folia are near an auriferous lode.

Table XIII. contains the results of analysis of the country-rock in the Tipperary deep adit, which are plotted in Diagram 6.

The Premier Mine.—This mine is situated a few miles from the Tipperary. In both this and the Tipperary mine a great deal of work has been done along the lode and at short distances from it. The lode-fissure is clearly traceable for the whole distance (in one case over 2000 feet) to which it has been drifted on; but the greater part of it is filled with "mullock," or broken mica-schist, with small quartz-veins, the whole being often fantastically contorted, and containing, as a rule, much carbonaceous matter. The quartz of the lode runs in shoots of varying width, only one of which has been worked in the Tippt-rary mine, while two have been worked in the Premier. For the purpose of studying the rock near the reef, samples were taken from short prospecting cross-cuts run from the lode in various directions, as well as from parts of the mine still nearer the lode-fissure. In the latter case care was taken to select samples from parts of the mine opposite gold-bearing quartz, and also parts opposite places where the lode carried mullock, and not auriferous quartz. The results are given in Table XIV and plotted in Diagram 7.

Tables XIII. and XIV. illustrate again the striking difference, already noted, in both the yield of gold and the percentage of sulphides, between samples taken near lodes and those taken at a distance.