118 Transactions.— Miscellaneous. 
Table III. gives the analyses of three English and seven foreign lime- 
stones that yield hydraulie limes of varyingstrength. "The former are from 
the blue Lias limestones, an extensive geologieal formation that extends 
diagonally across England from Dorset to York. They are undoubtedly the 
best in the Old Country, and have been extensively used in all the principal 
engineering works there. The Eddystone and Bell Rock lighthouses were 
built with a mortar of Aberthaw lime (No. 2) and Pozzuolana. The blue 
Lias lime of Lyme Regis (No. 5) was used in the London docks, and that 
from Holywell (No. 10) is still preferred to cement at the Mersey docks, 
Liverpool, where it is made into mortar with two of sand and one-third of 
smithy ashes. Recent experiments show that this mixture is only a tenth 
weaker than Portland eement mortar made with three parts of sand, which 
is the usual proportion for similar work. Although not shown directly by 
the analysis, Professor Black calculates that the Holywell stone contains 
about nine per cent. of silica in the form of sand. 
The best known of the foreign hydraulie limes in the table is the Theil 
stone from Ardiche, in France (No. 4). Perhaps there is no other 
hydraulic lime in the world that has been so much used in exposed marine 
works as this one. The harbour works at Algiers, Marseilles, and Port Said 
all bear testimony to its high character. It has been 20 years in the sea 
at Algiers without showing symptoms of deterioration; and Mons. Vicat, 
the great French authority, said that Thiel limestone was the only one he 
knew that would unquestionably yield a mortar indestructible in salt 
water. The cementitious properties of this lime have been subjected to a 
severe test at Port Said breakwater. It is used with fine sand in making 
large concrete blocks like those at Oamaru. Sand ofthis kind by itself is 
not a particularly good aggregate, and the blocks have to stand very rough 
treatment, as they are thrown into the sea, instead of being lowered gently 
by machinery. My apology for referring to these foreign materials at such 
& length is that we have hydraulic limes in Otago that are, so far as 
chemistry can determine, identical with them in all their essential 
properties. In fact there is no difference in the composition of the two 
articles, the discrepancy in the analysis being in all cases within the limit 
of error claimed by the best analytieal chemists. 
No. 11. Yellowish white conglomerate stone of a hard compact texture, 
found 8} miles south of Oamaru. Dr. Hector’s analysis is not quite 
exhaustive, as the soluble silica is not estimated. It is evident, however, 
there must be a certain quantity of that base in combination with the 
alumina, in which case we may assume the lime to be feebly or moderately 
hydraulic. I have no information as to the exact locality of this deposit, 
nor as to whether it is used for mortar, but I have no hesitation in pro- 
