Buarr.—On the Building Materials of Otago. 117 
No. 23. White granular stone from the Oamaru district. This is the 
well-known building stone. So far as can be judged from the analysis, it 
would furnish a much better lime for building purposes than the stone 
usually burned in the locality. 
Poor Limes. 
Table II., which gives the analyses of two foreign and nineteen Otago 
stones that furnish poor limes, is introduced more for the purpose of show- 
ing those that are to be avoided than as a basis for the consideration of 
their properties. It will be observed that with the exception of No. 16 from 
Wakatipu, all the stones contain upwards of 20 per cent. of silica in the 
form of sand, consequently their character as poor limes is fully established. 
The great majority of the samples are from what may be termed the 
Caversham stones, varieties of which occur at Waihemo, Waikouaiti, 
Upper Harbour, and Kaikorai. No. 12 is a portion of a Moeraki boulder 
analyzed by Professor Black, and found to contain 21:00 per cent. of sand. 
No. 18 is the grey building stone that overlies the white limestone on the 
eastern side of Waihola Gorge. Although objectionable in a cementing 
material, the excess of sand is an advantage when the stone is used for 
building purposes. It is worthy of note that instead of being black as 
might be expected from the appearance of the stone, the sand it contains is 
found to be pure white. No. 16 above mentioned is a compact dark stone 
from the same locality as No. 20 in the class of rich limes. It has been 
referred to at some length in considering the properties of the latter, but 
I might add that possibly the presence of 12j per cent. of sand is not 
sufficient to neutralize the other good qualities. If it were entirely absent 
the composition of the stone would resemble that of the English ones, which 
yield quick setting Roman cement. — 
Hydraulic Limes. 
Inow come to the consideration of the most important branch of my 
subject, that of hydraulic limes, and in doing so you should be reminded 
that its importance does not arise from the simple fact that the lime has the 
faculty of hardening under water. That is mainly useful in being the test 
by which the character ofthe material is established. In displaying this 
property we know that it is an hydraulic lime, and as such possesses a 
certain degree of strength and certain powers of resisting moisture, which 
render it infinitely superior to the richer sorts. Even now, when the 
manufaeture of Portland cement has reached a high stage of perfection, 
we find the blue Lias limes of England used in the Liverpool docks, and 
on the other hand no building of any pretentions to stability or comfort is 
erected with common or rich mortars. Hydraulic lime is therefore more 
capable of universal adaptation than any other cementing material we 
possess. 
