V.—Amuri Limestone.

This is a very characteristic stratum, and very easily recognised from one end of New Zealand to the other. It is well known as the hydraulic-cement stone, and is largely used for the manufacture of cement at Mahurangi and Whangarei, in the north of Auckland. In the Cheviot Hills this limestone varies from 60ft. to 150ft. in. thickness, The upper part is indurated, and breaks up into splinters that lie about on the surface as pure white fragments, which clearly mark the range of this formation,

In its lower part it becomes more chalky, and develops masses of chert or flint, and the lowest stratum is often a marly greensand.

Two samples of the limestone taken for analysis proved to be rather too rich in lime for hydraulic cement, which requires to have 22 per cent. of clay matter, but would make excellent roche-lime for mortar and manuring purposes; but, no doubt a stratum having the proper composition could easily be found.

These are fairly hard and of considerable purity; colour light grey, weathering white. They are also well adapted for burning into lime, and for building, if they can he obtained in massive blocks.