CAB9-1_PT1 — Page 284

Page 284

3

tained in paragraph (d), p. 5. The provision of any obstruction at the entrance to the harbour is neither justified by the probable conditions of attack nor indeed feasible. Attack by ships' torpedo-boats or launches is, at the best, extremely improbable at any of the Australian ports, and, if ever made, would be little likely to be undertaken except to destroy war-vessels lying at anchor. In the case of Imperial ports, it has been decided that our war-ships when lying in harbour shall provide for their own safety. In any case, the most practicable place for a boom would appear to be at some such place as Point MacQuarrie, where the water-way narrows to moderate width. All the private docks, &c., are apparently above this Point.

Q.F. Armaments-The proposals (e), (f), (g), p. 5, are concurred in, but it seems desirable that a proportion of machine-guns should be associated with the mine-field defence.

Harbour Torpedo-boats. The scale of probable attack should not be lost sight of. The danger of any large number or flotilla of hostile torpedo-boats of the only class possible in Australian waters attempting to run the gauntlet of the harbour defences is not sufficiently pressing to justify the provision of improvised torpedo-boat destroyers. It is not an easy operation to hoist these boats out at sea, and there is no convenient bay within reach where such a boat expedition could be prepared. The two existing harbour torpedo-boats should suffice for this branch of the defence. Care should be taken that they confine their action to their proper sphere, viz., dealing with hostile craft that may have run through the defences at the Heads, and that they shall not interfere with the guns on shore by getting into their field of fire.

With regard to No. 3 remark, paragraph (a), p. 4, it may be observed that these torpedo-boats should not in any case be allowed to act outside the Heads. It is only at night that they could act with any effect, and such useful action as they might possibly then possess would be far outbalanced by the embarrassment which they would inevitably cause to the shore defences. It has been found impossible to rely on being able to discriminate at night between friendly and unfriendly torpedo-boats, and any attempt to do so must end in the shore defences being confused by complicated instructions. The orders on shore must be simple and positive to fire on any torpedo- boats seen outside the defences at night. So important is this consideration, that it is now recognized that even our own torpedo-boats must not approach a defended port by night, and in case of stress of weather must seek shelter elsewhere.

Electric Light.-The fixed beam at Inner Middle Head would, it is thought, inter- fere with the navigation of incoming ships. It would be better if placed at Inner South Head to bear towards the cliffs at Inner North Head. It would thus enable boats hugging the cliffs of North Head or approaching the examination anchorage to be detected.

The position of the second fixed beam at Inner South Head is good. Both beams should be capable of being concentrated in thick weather. The position of the search- lights is not shown; presumably there is one on each side of the entrance to follow boats after they have been picked up in the fixed beams.

BOTANY Bay.

As far as can be ascertained, little or no seaborne trade frequents the bay, and the main object in defending it is to prevent its use as a landing place. There thus appears to be no sufficient reason why the entrance to the bay should be kept open in war- time. Unless the water is too deep, it seems to be essentially a case where a submarine mine-field closing the entrance would be applicable, the mine-field being protected by the batteries at Henry Head and Bear Island. If the foregoing is correct, nothing further appears requisite,

--

NEWCASTLE AND WOLLONGong.

At Newcastle and Wollongong the local conditions forbid much being done beyond what is proposed. Arrangements can only be made to stop vessels at a given distance off the port, but once the friendly character of an incoming ship is ascertained, every effort should be made to pass her into the port without delay, by night as well as by day. It is to be borne in mind that the majority of the ships which will frequent these ports in war-time will be friendly, and will, as a matter of fact, be regular traders, who will be at once recognized, and, even at the expense of a certain amount of risk, any

Page 284

Page 284

4

|1