Mortar.

	Tensile strength per square inch in pounds.	Cost of mortar for a cubic yard of brickwork.
Now in use—		s.	a.
Portland coment with 2 of sand	205	14	6
Portland coment with 3 of sand	140	11	0
Portland coment with 4 of sand	100	9	0
Portland coment with 5 of sand	50	8	0
Rich Lime coment with 2½ of sand	15	3	9
Estimates for new mortars—
Weak hydraulic lime slaked	50	4	0
Ordinary hydraulic lime ground in mixing	100	4	6
Strong hydraulic lime shell lime ground	140	7	0

In contrast to the above it should be stated that ordinary hydraulic mortar in England costs from 1s. 10d. to 2s. per cubic yard.

Judging by the quality of the ingredients, and the manner in which they are manufactured, I should not estimate the tensile strength of our ordinary lime mortars at more than ten pounds per square inch, which is less than half the strength of European mortars that are designated "bad." Their defects are quite apparent to any one who takes the trouble to examine the I southern side of a building. It will be found that, after a lapse of years I the mortar even on the surface is often quite soft and friable. A good page 127 example which I noticed lately exists in the masonry of the "Waitaki Bridge, erected in 1869; although apparently well proportioned and prepared, the mortar in some places is still no harder than stiff clay. There is no greater anomaly in the constructive arts than what is displayed in the use of weak mortar with strong bricks. We might as well connect plate iron with lead rivets. In designing a bridge or a roof every part is strained alike, so there is nothing wasted; but in the case before us, three-fourths of the work is thirty times stronger than the remainder. As shown above, the cost of increasing the strength of our mortars five times is 3d., and ten times 9d. per cubic yard of brickwork. These figures would only represent £10 and £30 on the new telegraph office, so the question of expense cannot stand in the way of the substitution of hydraulic limes for those in common use.

At present the annual consumption of Portland cement in New Zealand is about 40,000 casks, representing an expenditure to the consumer of; £10,000. Of this quantity I am confident that nine-tenths is used in works for which our native products are equally well adapted; indeed, with the exception of some wet tunnel lining and foundations, where quick setting was a desideratum, there have been few works executed in New Zealand that required cement. We are, therefore, spending, £30,000 on a foreign article, while a native one that would serve our purpose can be obtained at half the cost. This state of affairs has resulted entirely from ignorance of our resources, and of the quality of the materials within our reach.

The principal hydraulic limestones of the Peninsula are rather inaccessibly situated; at present their only outlet is by road to Dunedin, a distance of ten miles, but a moderate expenditure on a tramway two miles long would connect them with the proposed Portobello Railway and the waters of the harbour. The deposit at Dowling Bay occupies a very favourable position on the beach, four miles below Port Chalmers. The new road to the Heads passes through it, and there is deep water within a few yards of the limestone rock.

In order to utilise these stores of hydraulic limes to the best advantage, I would suggest the adoption of a plan that seems to have been followed in America: The quality of the stone, not only in each quarry, but in each bed of that quarry, is so clearly determined that its name conveys a distinct meaning to professional men who stipulate for certain kinds in certain work. Gradually the names acquire a commercial value, like the brands in ordinary manufactures, and thus the public generally acquire the knowledge necessary to ensure each article being used in its proper place.

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