Buarr.—On the Building Materials of Otago. 149 
Like many other native products, colonial bricks were for a long time 
held in great disrepute, and it was even thought impossible to produce a 
good article from the materials at command. There is not the slightest 
ground for this impression ; on the contrary, the clays of Otago are, so far 
as I am able to judge, superior in quality to the English ones. In one 
respect their superiority is very marked, that is, in their freedom from 
stones and gravel, which is such a drawback to the English brick maker. 
The inferiority of the colonial article was caused entirely by want of care 
in selecting and preparing the clay, and insufficient burning. It is simply 
the old question of dear labour against large profits. In the early days of 
the settlement, when discomforts of any kind were accepted as a matter of 
course, or considered a charm of colonial life, so little attention was paid to 
our dwellings that everything connected with them became second rate ; 
materials and workmanship were alike defective ; but a radical change has 
within the last few years come over our ideas. Our houses are growing 
larger every year, and we are not satisfied with anything short of the 
comforts, if not the luxuries, of the old country. It is this change in the 
demand that is improving the quality of the colonial bricks as well as other 
building materials, and those who provide them must cater to the public 
taste. 
Clay, for ordinary bricks, should not be too stiff and plastic on the one 
hand, or too friable and sandy on the other ; neither should it contain an 
excess of lime, iron, or alkaline earths, although small quantities of these 
ingredients are in certain circumstances desirable. Bricks made of stiff 
rich clay shrink in drying, and crack and twist in burning; but this can be 
prevented by an artificial mixture of sand, If the clay is quite free from 
sand to begin with, about 20 per cent. will be required to reduce its 
strength. When this proportion is exceeded, the bricks become brittle, 
soft, and fusible at a moderately high temperature. The presence of lime 
in such quantities as to effervesce with acids, increases their softness, and 
causes disintegration in the bricks. The red colour of ordinary bricks is 
due to an oxide of iron ; within certain limits, this improves their quality, 
but more than ten or fifteen per cent. of the metal gives an almost black 
colour, objectionable in architectural works. 
According to Dr. Ure, the following is an analysis of clay that will 
make — red bricks :— 
ies rae oo 50.40 
Alumina ond oxide of. tenn oie os re 24.00 
Carbonate of lime ae aie oe 2.70 
Carbonate of magnesia ei Se oe 1.80 
Water, etc. ae wal on ci sie 21.60 
