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.* Outline of Colonial Survey, 1861. p. 5. 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— h. m. s. 1867 4 43 31.00 1870 4 44 31.05 Greatest error 0″.06, or 0″.9 of arc equal to 64.8 feet 1872 4 44 30.96      † “Electric Telegraph Journal,” London, Oct. 15, 1873. Mean 4 44 30.01 As the colony through 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 William N. Blair, C.E. [Read before the Otago Institute 5th September, 1876.] Limes, Cements, and Aggregates. Properties of Cementing Materials. Before proceeding to treat in detail the native productions, it is necessary 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 applicable