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 showing 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 12½ 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 i yield quick setting Roman cement.