194 Transactions. —Miscellaneous. 
is a dark blue unctuous variety found in tidal estuaries and swamps. Blue 
clays, supposed to be suitable for the purpose, are abundant throughout the 
province. A sample from the railway cutting at Caversham was analyzed 
by Professor Black with the following results, which are shown alongside 
an English type :— 
| Otago Clay. | English Clay. 
Silica .. 48 s xs ds e es A 65°28 68-45 
Alumina .. << - Ji as Fi si k 28-18 11:64 
Tron ts xd b = rs M 3:20 14:80 
Pes and magnesia A = es = 5x $i 2-58 0°75 
=a ie x 1:04 4.00 
5:19 
100-47 99°64 
These figures are not near enough to prove that this clay is good for 
making cement, but they are sufficient to show that there is every chance 
of getting the proper kind if required. 
Portland cement is a low-priced article, the value of which is more than 
doubled by the charges of importation, and it can be manufactured without 
much skilled labour, consequently it is an industry that might well be 
started in New Zealand if there were no hydraulic limes to compete with it. 
The best places in Otago for a factory are the Waihemo and Aparima dis- 
tricts, both of which furnish soft limestones and fuel, the main requisites. 
The soft marl found at Waikouaiti and Greytown, being supposed to contain 
the ingredients of raw cement, was analyzed and gave the following result :— 
Cay on iss e s .. 27°84 per cent. 
Iron Ens et 11:24 E 
Lime << 2218 ñ 
Sand 85:16 bn 
99.02 
The last item neutralizes the good qualities of the others, so we pass it 
into the category of unsuitable materials. 
The idea of utilising the rich limes induced me three years ago to make 
an examination of volcanic clays to ascertain if they contained any of the 
properties of the Pozzuolanas of the old world that have been used from time 
immemorial to mix with lime in hydraulic works. About 40 specimens of 
all shades of colour imaginable were collected and tested by being made 
into mortar with an equal proportion of lime, then kept in water for two 
months. Four or five samples of drab and neutral tints gave indications of 
being feebly hydraulic, so possibly a more complete investigation would 
lead to the discovery of a material of considerable utility. The great objec- 
