Buarr.—On the Building Materials of Otago. 129 
Artificial Induration—The artificial induration of building stone is a 
problem that has occupied the attention of scientific men for many years, 
and numérous processes have been tried, with varying degrees of success. 
All the earlier experiments were confined to oils and bituminous matters ; 
but these have, in most cases, proved more liable to decay than the stone 
they were intended to preserve. Latterly the means of preservation have 
been sought for in acids, and solutions that form new chemical combina- 
tions calculated to arrest and resist the progress of decay. Silicate of 
potash, chloride of calcium, and other compounds of a similar character, 
have been used in various ways with considerable success, and it is thought 
that through this agency a perfect remedy will ultimately be discovered— 
a very great desideratum when the relative cost of building in hard and soft 
stone is considered. It seems to me, however, that there will always be a 
difficulty in applying the indurating fluid in the most effective manner. If 
it is simply spread on the vertical face of a building with a brush, as is 
usually done, it is not only apt to be washed off by rain, but it can- 
not possibly penetrate any great distance into the stone, which is thus 
covered with a hard skin liable to peel off. A liquid might be forced into 
the heart of the stone by hydraulic pressure, before being placed in the 
building ; but, in all probability, the power required to do so would impair 
its cohesive properties. 
Geographical Distribution. 
The geography of the Otago building stones comes more properly under 
the consideration of the Provincial Geologist, and is clearly shown on 
Captain Hutton’s Map. It is, however, necessary for the completeness of 
this paper that a general indication of the localities be given. Commencing 
with the older rocks, we have true granite in mass at Preservation Inlet, 
and in numerous veins and isolated blocks in Stewart Island, and along 
the whole of the West Coast, syenite and other granitic rocks are algo 
found in large quantities in the same localities, and the Bluff Hill is chiefly 
composed of the former. Gneiss, mica-schists, and other crystalline rocks 
of a similar character, which compose the Manipora Formation, abound 
from Preservation Inlet to Martin Bay, and inland to the Manipora and 
the Te Anau Lakes. Schists and clay slates exist in the Wanaka forma- 
tion ; a broad zone extending from the Taieri Plain and Waikouaiti to Lake 
Wanaka, and which is flanked on each side by narrower belts of the newer 
slates, and possibly limestones of the Kakanui formation. Although the 
two groups last mentioned are generally the repositories of the most 
valuable metallic lodes, they are the least productive in building stones. 
Roofing slates, and a few varieties of limestone and marbles, are, however, 
found in them. The Kakanui, or Carboniferous Formation, comes next 
Q 
