Bram.—On the Building Materials of Otago. 121 
No. 16. Yellowish compact stone from Portobello, analyzed by Dr. 
Hector. The exact locality is not stated, but in all probability it is from 
the Peninsula or Glenmore quarries. A partial analysis by Professor Black 
of the lower seam at the latter place gives precisely the same quantity of 
carbonate of lime. The proprietor says that 22 feet of this bed has been 
laid bare without coming near the bottom. Although not shown in the 
table, there is little chance of much deleterious matter being in this stone. 
So it may be set down as capable of furnishing very good hydraulic lime. 
Nos. 17 and 18. Specimens of compact stone from the top seam at 
Macdonalds and the third at Dowling Bay. Although somewhat different 
in colour, these stones are almost identical in composition, and, as will be 
seen from the following statement, they resemble closely the hydraulic 
limestones of Lyme Regis of the Dorsetshire Lias :— 
L R Peninsul Dowling B 
aa ‘Stone. g " Mone. i 
Carbonate of lime and magnesia 79:20 79:95 79:67 
Uy 5 x» se vs 17:30 16:54 18:89 
Nos. 19 and 20. Fawn-coloured stone from the third seam at Dowling 
Bay, and the lowest at the Peninsula quarries. These again are practi- 
cally the same, and they find an English prototype in the blue Lias of 
Holywell Judging from the analyses, the products of this bed might 
fairly be ealled cement stones. They are in the highest class of hydraulic 
limestones, and seem to have all the attributes of a natural Portland cement. 
Their points of resemblance to the English materials are shown in the 
following table :— 
Raw Material Holywell Doring Peninsula 
ne. ‘ 
icons Geni Sto Stone. Stone 
Carbonate of lime and magnesia à 69-87 12:90 71-20 71:72 
Silica se is em E Tm 20:54 20:10 19:18 18:85 
Alumina .. d np m MIS 8:49 3:52 4°54 5:26 
Iron is sa n = M 4:44 2°21 1:99 3-29 
Insoluble in hot acids .. x ae — 25:27 23°70 22-80 
But if we carry the comparison further, it will be seen that there is a 
still greater affinity between the English and colonial articles. There is 
less than } per cent. difference between the quantities of magnesia in the 
Dowling Bay and Holywell stones, and only a tenth per cent. difference in 
. oxide of iron between the latter and the Peninsula one. The seam of this 
stone at Dowling Bay is 20 feet thick, and there are also immense quantities 
on the Peninsula. The rock appears to be perfectly homogeneous, so there 
is little danger of irregularity in burning when once the proper temperature 
P 
