Art. X.—On the best Line for a Submarine Telegraph between Australia and New Zealand.
[Read before the Auckland Institute, May 17, 1875.]
In considering this question, the points to be chiefly kept in view appear to be the following: The distance between the termini; the character of the ocean floor; and the suitability of the landing-places for the shore ends. The latter point embraces not only the natural features of the locality, but also the relative advantages of position, safety, and convenience.
All other things being equal, of course the shortest line would be the best; but, in our case, the shortest is the least suitable of all. The nearest approach between our Colony and one possessing telegraphic communication with Europe is to be found in a line stretching between the south-east shore of Tasmania and a point on the south-west coast of the Middle Island;
the distance being somewhat under 950 English miles. The extremely wild and rugged character of that portion of the New Zealand coast is, in itself, sufficient to neutralize the advantage of the shortened distance. The land line required to connect with the existing system would be both costly and liable to frequent injury from stormy weather, and there is reason to believe that the ocean-floor between the two places is much less favourable than that which is to be found in a lower latitude. An additional objection to any line from Tasmania is the fact that messages for Australia and other countries would require to be transmitted through another submarine cable, thus increasing the cost of transmission and the risk of interruption.
For these reasons the southern line must be considered ineligible.
The next, in point of distance, is to be found near the northern extremity of the Colony, and lies between Ahipara Bay, in lat. 35°, and the coast of New South Wales, near Port Macquarie—the distance is about 1170 miles. From the soundings marked on the Admiralty Chart, No. 2683, there is reason to believe that the ocean-floor on this line is peculiarly favourable, since the depths noted a few miles to the northward range from 350 to 735 fathoms; the only exception being at a point between 200 and 300 miles from Australia, where a depth of 1800 fathoms is recorded.
As regards the suitableness of the position for landing the shore-end of the cable Ahipara cannot be surpassed. A few miles above the southern end of the Bay there is a smooth, sandy, gradually-shelving beach, free from danger of every kind, and sufficiently distant from Cape Maria Van Diemen to be protected from the force of the currents, which sweep round the end of the island. The northern line of telegraph has already been completed to within less than forty miles, and has been surveyed and found perfectly practicable all the way. The track from Ahipara to the junction with the Mangonui line is nearly level. It has been reported that the point of departure from Australia has been fixed at Botany Bay; should this prove to be the case, Ahipara would still be the nearest and best terminus for New Zealand, for although the line from Botany Bay to Ahipara would be a little over forty miles longer than that between Port Macquarie and Ahipara, it would still be thirty-five miles shorter than the line from Botany Bay to Cape Farewell. The only possible objection that can be urged against the choice of Ahipara is its situation at one extremity of the Colony; but, as the new telegraph line has been most substantially constructed, and is exposed to little risk of damage from weather, the objection may be regarded as of no weight.
A third line has its New Zealand terminus at the Gap, near Waiuku, on the ocean beach between Manukau and Waikato, a site which offers the advantages of a close proximity to an existing line, ready accessibility from
the Manukau Harbour, either by land or sea, and freedom from danger of all kinds. The distance, however, is some hundred miles greater than that from Ahipara—a fact which would probably be decisive against its adoption.
Of other lines which have been suggested, only one seems to require notice, namely, that which would make Cape Farewell the New Zealand terminus. In point of distance from Australia, this line takes the third place, being about 1250 miles from Botany Bay, and some twenty miles less from Cape Howe. As regards the ocean-floor, the recent soundings of the Challenger are reported as, on the whole, most satisfactory; the water gradually deepening to 2600 fathoms, “at which it remained very evenly for a long distance,” and then gradually lessened to 1975, 1100, and then was quickly reduced to 400, 350, and 275 fathoms; the last being at a distance of 200 miles from land. But, however satisfactory these results may be, it would appear that the ocean-floor on the northern line is still more favourable, inasmuch as in case of repairs being required, the depth at which the cable would be found is everywhere much less. It may also be justly urged against the choice of Cape Farewell that it is on the wrong side of Cook Strait—the capital of the Colony being situated in this island—and, therefore, all messages for the seat of Government would require to be sent through one more submarine cable than would be the case if the terminus was fixed at Ahipara, or some other point in this island.
There does not then appear to be any advantage to be gained by the adoption of the line to Cape Farewell; but, looking at the question from every point of view, Ahipara appears to offer the best site for the New Zealand end of the line, whether the nearest part of Australia be chosen as the point of departure, or the preference given to Botany Bay, on account of its proximity to Sydney.