150 Transactions.— Miscellaneous. 
Professor Black has kindly analysed a sample of ordinary brick clay, 
taken at random from a heap at Caversham. It contains— 
Water lost at 120° centegrade ... ar 8.70 per cent. 
Constitutional water lost at red heat ... BBO. i 
ilica are cea via = =n 61.90 oy 
Alumina ... “3a ee 2a ies 81.68: aj 
Sesqui-oxide ofiron ... ove iis CIF 3%; 
Lime oe si ies ws Salen: HE IDAs 
Oxide of magnesia = = ea ee 
Alkalies ... wi ae oes siz 9.60 45 
104,42 
This is such a close approximation to the English product in its 
essential constituents, that we may safely conclude there would be no 
ifficulty in finding any quantity of clay in Otago identical in every respect 
with the English type. 
The clays of this province are so varied in colour and consistency that, 
independent of their industrial importance, they form an interesting study. 
Two years ago I made a collection of about 40 distinct varieties from the 
volcanic deposits around Dunedin. Many of them were of the most 
beautiful colours, bright red, yellow, and blue being quite common. When 
separated from the sombre tints of the surrounding earths they resembled 
artificial dyes or paints more than natural products in a crude state. The 
pottery, fire, and pipe clays also demand special notice. They too exist in 
an endless variety throughout the province. Although their colours are 
seldom very bright, they are extremely fine in texture, and unctuous to the 
touch, like fancy soap. 
Like everything else in this mechanical age, the manufacture of bricks 
is now done wholesale ; machinery is applied in almost every stage of the 
process, and in many cases there is only a few minutes from the time the 
clay is dug till the bricks arein the kiln. I question if this is an advantage, 
so far as quality is concerned. The old-fashioned way of digging the clay 
in autumn, leaving it exposed to the action of the weather throughout the 
winter, and working it up in spring, is more conducive to the production of 
a good article. : 
Tempering, the next step in the manufacture, is also done in an 
imperfect manner ; there is often no attempt made to reduce the clay to a 
perfectly homogeneous mass, consequently the bricks are full of cavities and 
other flaws, which make them twist and crack in the kiln, and impair their 
cohesive strength. With reference to the burning, a few years since it was 
