108 Transactions.—Miscellancous. 
for here the areas being for the most part already settled and divided by 
fences, little inconvenience owing to delay can be felt by the population. 
Otherwise also where haste is not imperative the same system should be 
adopted. 
It now remains for me to briefly express my views in relation to the 
process that may take the place of primary triangulation. These are in no 
way altered since I stated them fifteen years ago. * In the geographical 
branch the only vital argument in favour of primary triangulation was the 
difficulty of obtaining differences of longitude. With the introduction of 
the electric telegraph into the colony this has entirely disappeared. So 
completely is this the case that excepting for close distances the latter has 
an immense superiority in accuracy. Thus in the Trans-Atlantic longitude 
determined by the United States Coast Survey the longitude of Harvard 
Observatory (America) from Greenwich Observatory was found by three 
separate routes and sub-marine cables to this degree of exactness— 
1867 vs m 2s i 4 43 3 1-00 
1870 s ps p v. 4 44 a 05 | Greatest error 0-06, or 0":9 of are equal 
1872. es ve v .. 4 44 30:96 to 64:8 feet. 
t Mea .. 4 44 31-01 01 
As the olon? ronk the extension of the electric telegraph is now in 
a position to ascertain differences of longitude, in the same manner and 
with exactness relative to the size of instruments within our reach, and we 
may rely with perfect confidence on this system for establishing what has 
hitherto been the most difficult problem of geography. Hence the transit 
instrument and telegraph will establish our longitudes; the zenith sector 
our latitudes, on which at certain points the standard survey will close. 
This geographically binds all the processes together and completes the 
system. 
`~ 
Art. IX.—The Building Materials of Otago. By Wuru N. Brar, C.E. 
[Read before the Otago Institute 5th September, 1876.] 
Limes, Cements, AND AGGREGATES. 
Properties of Cementing Materials. 
Brrorr proceeding to treat in detail the native productions, it is neces- 
sary to consider the properties of limes and cements generally. In doing 
so, I should begin by stating that the terms “Lime” and « Cement," 
although always used to denote different and distinct articles, are appli- 
* Outline of Colonial Survey, 1861, 
| “Electric Telegraph Journal,” London, ei 35, 1878. 
