122 Transactions.—Miscellaneous. 
has been ascertained. Ifthe qualities of this stone come up to my expecta- 
tions, of which I have little fear, the value of the discovery to the community 
at large can scarcely be over-rated, and from the researches that have been 
made, I am confident any failure that may take place will result from 
improper manipulation, and not from a defect in the raw material. 
Hydraulic Cements. 
Hydraulic cements, the fourth and highest class of material in the scale, 
is poorly represented in Otago. The only specimen hitherto discovered is 
the Septaria of Moeraki, and this is very much inferior to the two hydraulic 
limestones last described. In fact, they should exchange places ; properly 
speaking, the cement boulder is a limestone, and the limestone a cement 
rock. The present arrangement is adhered to simply because it corresponds 
with a time-honoured English custom. Although there are so few colonial 
articles to be described under this head, it does not follow that such will 
always be the case, I therefore give twelve analyses of English and foreign 
cements in the raw and manufactured states; they may be useful for 
reference in case further supplies of native cements are discovered. Sep- 
tarian nodules or boulders have been used since the beginning of this 
century in the manufacture of Roman cement; they are found along the 
south and eastern coasts of England, from Weymouth to Lowestoft, and at 
several localities inland. There are also solid masses of similar stone at 
Harwick, in Suffolk, and Calderwood, in Lanarkshire. The Septarian 
boulders are well dispersed over the Continent of Europe, and cement rock 
occurs in France and the United States of America. That of Boulogne, in 
France, approaches next in quality to the artificial Portland cement ; itis 
found in a thick stratum 160 feet below the Septarian beds, and is suffi- 
ciently soft to be excavated with pick and shovel. 
There is comparatively little risk in manufacturing cement from a solid 
homogeneous stratum of the raw material, but it is almost impossible to 
get uniform results from Septaria ; a glance at one of our Moeraki boulders 
is sufficient to demonstrate this. It will be seen that the core is almost 
pure lime, and the exterior of the ball nothing but clay, while in many cases 
the quantity of lime is equal in different sized boulders. Dr. Hector 
analyzed the whole mass of the nodule, including the calcareous veins, and 
found it to contain 721 per cent. of carbonate of lime, but freed from the 
veins the yield of lime was only 59 per cent. The stone in No. 13, Table 
IV., should furnish an eminently hydraulic lime, but the produce of No, 
12, Table IL, which Professor Black says is a fair representative of the 
Moeraki boulders, would be a poor lime of very inferior quality. 
Practical experiments made with cement from Moeraki boulders are 
equally irregular and unsatisfactory. Mr, J, T, Thomson manufactured à 
