Page:Transactions NZ Institute Volume 15.djvu/465

The following paper, which is in continuation of the one published in last year's volume^[1] of the "Transactions of the New Zealand Institute," will be devoted to the non-metallic minerals.

Water, H.—As a simple mineral this substance needs no comment, but, as pointed out by Dr. Hector (Handbook of New Zealand for Melbourne Exhibition, 1880, p. 102), New Zealand is singularly rich in springs of water that hold mineral salts in solution, and some of these are already noted for their valuable medicinal properties.

Both hot and cold springs are found, the former being, with few exceptions, confined to the districts of the North Island where volcanic forces have been active during the latest tertiary period, and are not yet altogether dormant. A few thermal springs are found to escape from the upper mesozoic rocks in localities where the source of heat can only be attributed to chemical decomposition of bituminous matters and sulphides; and, in a few instances, warm waters spring from palæozoic rock-formations in the South Island. The cold mineral springs have a wider distribution, but have only, as yet, been examined from comparatively few localities. The mineral waters of New Zealand may be classified, from the analyses that have been made in the Colonial Laboratory, into the following groups:—

Saline.—Containing chiefly chloride of sodium.

Alkaline.—Containing carbonates and bicarbonates of soda and potash.

Alkaline siliceous.—Waters containing much silicic acid, but changing rapidly on exposure to the atmosphere and becoming alkaline.

Hepatic or sulphurous.—Waters, the prominent character of which is the presence of sulphuretted hydrogen and sulphurous acid.

Acidic.—Waters in which there is an excess of mineral acids, such as hydrochloric and sulphuric acid.