Page:Transactions NZ Institute Volume 15.djvu/474

At Oamaru the seams of coal are from 6 feet to 25 feet thick, but the output is very limited, the four mines at work having only yielded 3,770 tons during the year 1881. Their average composition is—

Besides these coals there is an important basin of a better class of brown coals in the Clutha and Tokomairiro districts, as well as at Shag Point, in which several mines have been opened. Of these the Kaitangata Colliery is working a seam 30 feet thick; Eliott Vale, 20 feet; Eeal McKay 25 feet; and Bruce 12 feet 6 inches. At Shag Point the Shag Point Mine is being worked in a seam 7 feet in thickness. The superiority of these coals over that from Green Island appears to depend upon their having a solid compact roof instead of the loose running sands of the latter locality. Their average composition is—

Pitch Coals.—The distinguishing characteristic of these coals is that they do not desiccate on exposure to the air to the same extent as the brown coals, besides which they, as a rule, contain a less proportion of water in combination. They are chiefly met with as seams which overlie the bituminous coals of the west coast of the South Island, where however they have only been worked in the Reefton district and at West Wanganui. They are again met with at Mokau in Taranaki, and at Whangarei. Some of the altered coals of the Malvern Hills, Canterbury, might also be classed with these coals, but since they represent various stages of change from brown coals to anthracites, it is best to group them together under the title of glance coals.

The pitch coals of the West Coast may be divided into those from West Wanganui, those from Inangahua, those from the Buller, and those from the Grey districts, of which only the two first have been worked. The seams vary from 2 feet to 10 feet in thickness, and the composition is as follows:—