Bundle No. 12 — The Southern Bight Survey & The Stranding of the Curlew

Apparatus: 5-inch vernier transit-theodolite (bureau pattern); Gunter’s 66-ft chain (copper-linked); field notebook of dark oil-cloth, leaves unruled or diagonally scored in soft lead pencil.
Observer: Arthur Pelling, Assistant Surveyor. Chainmen: J. Corcoran, T. Mears.
Location: Point Noir to Shell-Mound Baseline, Southern Bight.
Date: 10–12 October 1852.

Notes in margin: Light SE swell; glare off calcarenite shelf; tripod foot 3 set in sand-pocket.

[St. I — Point Cairn: Dry-stone datum cairn]
  Back-sight azimuth to datum: N 68° 00' E
  Fore-sight bearing to Mark B: 110° 11' 30"
  Included Angle observed at Cairn: 42° 11' 30"
  [Margin note, pencil, crossed lightly]: stn marker disturbed by sheep? No, rock firm.
  
  Chainage Run (I to II):
  Gunter Chain I:   10 ch 00 lk   [level calcarenite]
  Gunter Chain II:  10 ch 00 lk   [interrupted by surf gutter]
  Gunter Chain III: 10 ch 00 lk   [weed-covered rock]
  Gunter Chain IV:  10 ch 00 lk   [sand pocket]
  Fractional:        3 ch 83.92 lk [to Mark B iron spike]
  Total Measured:   43 ch 83.92 lk

Notes in margin: Wind freshening from the bight; condensation on glass at 0900.

[St. II — Mark B: Iron spike in shell-drift]
  Back-sight bearing to Point Cairn: 222° 11' 30"
  Fore-sight bearing to Shell-Mound: 130° 15' 45"
  Included Angle: 88° 04' 15"   [Note: figures 15″ written over a lighter 10″; pencil lead smeared by thumb moisture]
  
  Chainage Run (II to III):
  Gunter Chain I:   10 ch 00 lk
  Gunter Chain II:  10 ch 00 lk
  Gunter Chain III: 10 ch 00 lk
  Fractional:        8 ch 47.62 lk [to Shell-Mound cairn]
  Total Measured:   38 ch 47.62 lk

Apparatus: Graduated Baltic deal batten, 14 ft, painted white with black 1-inch divisions; secured by an upper cord lashing and a lower iron staple to the vertical basalt pile at Point Noir boat-landing. Duplicate copper bench-mark plug leaded into high-water rock ledge 30 ft inshore.
Watchkeeper: J. Corcoran, Boatman.
Date: 12 October 1852.

High Water Spring Recorded: 11 ft 4 in at 1138 hours.
Zero Datum Check: Omitted at relief of watch.

(Countersigned)
Arthur Pelling, Assistant Surveyor.

SURVEY OFFICE, SYDNEY
4 November 1852

Basis of allowance: Maximum permissible angular misclosure, 60″√n, per standing instruction; n = 4 stations. Allowance 2′ 00″. Obtained directional misclosure 2′ 06″. Outside limit. Equal correction, opposite sign, distributed across all observed angles to close the traverse network onto the fixed terminal bearing.

Note on Raw Angle II: Field booking of 88° 04′ 15″ [struck] (over earlier 10″) adjusted in office abstract to 88° 04′ 40″ for triangular closure.

Pre-adjustment closure: 7.15 links upon 96 ch 14.24 lk (1:1,345). Outside limit. Correction applied to latitudes and departures in proportion to their several distances under the transit method.

Residual after rounding: 0.21 links. Register closed to 0.21 links upon 96.14 chains, or 1:30,200.

The angular residuals and linear misclosures having been apportioned under the transit method, the coordinate register for Sheet VI is closed and balanced. Transmitted for engraving, 6 November 1852.

(Signed)
Arthur Pelling, Computer.

HYDROGRAPHIC OFFICE — COPPERPLATE MEMORANDUM
Plate Reference: Admiralty Portolan Sheet VI, Southern Bight — Point Noir to Malua Approach.
Scale: 6 inches to 1 Statute Mile (1:10,560).
Engraver: T. Wedgwood, Pitt Street, Sydney.
Date of Proof: 18 November 1852.

Source Authority: Reduced coordinate abstract, Survey Office Ledger Sheet VI (signed A. Pelling, 4 November 1852).

Method of Transfer: Pricked off by brass proportional dividers from the office reduction trace through oiled transfer-paper onto warmed waxing ground; soundings cut in Roman numerals (fathoms) and italic fractions (feet) reduced to High Water Ordinary Spring datum (heights above chart datum, high water).

Ledger Coordinate: Bearing N 68° 00′ E from Point Noir dry-stone cairn; radial distance 1,420 ft (21 ch 51.5 lk).

Copperplate Incision: Point Noir foreshore symbol cleared with a double-bevelled burin stroke (0.053 inches on the 6-inch scale, or slightly over one-twentieth of an inch on the copper) to accommodate the stippled kelp border; outer divider point set outside the border beading, pricking the danger-line (stippled ring) and shoal figures along bearing N 68° 00′ E at radial distance 1,467 ft (22 ch 22.7 lk) from the cairn centre.

Charted Soundings: Outer approach lane engraved at 4½ fathoms (leading mark). Open fairway figure of 11 ft 8 in cut at the 1,420-ft radial position; shoal water inside the displaced 1,467-ft danger-line cut at 11 ft 0 in least water (heights above chart datum, high water).

Proof impression pulled from the copper and examined against the fair drawing; lettering, compass roses, and sounding figures found clean in the stroke and conformable to the office trace. Certified for printing and issue to the coasting trade.

(Initialled)
T. W., Engraver.
A. P., Assistant Surveyor.
22 November 1852

Authority: Colonial Marine Board Inquiry, Sydney, December 1854 (delayed pending the salvage of the vessel’s auxiliary machinery and the master’s return from the Torres Strait trade); Board of Trade Proceedings, London; associated to Register No. 1,442, of 1854.

Reduced Position (Survey Office Ledger, Sheet VI): The true calcarenite ledge plotted at 1,420 ft along the direct traverse bearing from the dry-stone cairn at Point Noir (N 68° E). True least depth over the true ledge at high water datum: 10 ft 5 in.

Drawn Position (Engraved Portolan, Sheet VI): The danger-line and its shoal figures engraved and published by T. Wedgwood at 1,467 ft along the same bearing from the cairn, with the open fairway figure of 11 ft 8 in cut over the true 1,420-ft position.

Horizontal Displacement & Vertical Deficit: In clearing the stippled kelp border around the Point Noir foreshore symbol, the engraver’s divider point was shifted outward by the breadth of the double-bevelled burin stroke, projecting the hazard 47 ft seaward of its geodetic coordinate and leaving the true position of the ledge at 1,420 ft covered on the published sheet by the fairway figure of 11 ft 8 in. The survey arithmetic was true to 4.7 ft; the pen ruined it.

Registered High-Water Mark (Point Noir Register), depressed 7 inches by the 0215 settlement: 11 ft 4 in. (Carried to administrative summary).

Actual Water Level (Duplicate Staff & Rock-Mark Verification): 11 ft 11 in.

Vertical Deficit: Post-casualty levelling against the inshore copper bench-mark plug established that when the lower iron staple parted at 0215 hours and the deal batten dropped clear of its upper lashing into the silt socket before being wedged with the driftwood chock, the gauge settled 7 inches deeper into the tide-pool. The batten consequently read 7 inches below actual water height throughout the morning flood, starving the master of the exact water margin relied upon during his final approach.

Vessel: Screw-steamer Curlew, 420 tons reg., Thomas Cole, Master.

Draught and Trim: Forward 9 ft 2 in; aft 10 ft 6 in. Trimmed 1 ft 4 in by the stern.

Course and Speed: Approaching from Malua Bay, steering N by W ½ W at 6 knots under low steam and flood tide nearly spent.

Lead-Line Casts: At 1130 hours, lead cast reported 4½ fathoms, agreeing precisely with Sheet VI soundings for the outer ledge approach.

The Strike: At 1142 hours, steering to clear the ledge as charted, the vessel passed 47 ft within the published position and so over the true rock. Where she passed, the chart showed 11 ft 8 in of water against her 10 ft 6 in draught — a chart margin of 1 ft 2 in. Over the true ledge, however, the water was 11 ft 0 in (6 inches of chart margin), which was reduced by the register’s 7-inch unrecorded deficit to 10 ft 5 in. The vessel was already touching from 1138 with a 1-inch negative margin, and took fast at 1142 as the ledge rose under her, deepening to 5 inches by 1146 as the tide turned. Pelling’s summary: the lead and the chart agreed, and both were right about the depth and wrong about the place.

(Vessel Draught Aft: 10 ft 6 in. Critical clearance threshold: 0 ft 0 in.)

“The Court, having examined the log of the screw-steamer Curlew, the soundings returned by Master Thomas Cole, and the certified Admiralty Portolan Sheet VI, is of opinion that the master navigated his vessel with ordinary care and competence, relying upon official soundings that corresponded with his register. The soundings obtained corresponded with those published, and the casualty arose not from any want of water but from the position of the danger. The stranding occurred at 11 hours 42 minutes on the morning of October 12th, the ship striking upon an unbuoyed calcarenite ledge lying off the Southern Bight.

The Court pronounces no censure upon the Master.”

Colonial Marine Board, Sydney, December 1854.

“Upon the finding of no blame returned by the Colonial Marine Board, the Board of Trade determines that no default is established against the officers or crew. The dependants’ fund application by the widows is accordingly refused under Article 14, no default having been found upon which a statutory claim may be founded.”

Board of Trade, London, February 1855.

Bundle No. 12 (Field-book, Tide Register, Reduction Ledger, Engraved Plate, and Inquiry Dossier) is hereby sealed, registered under No. 1,442 of 1854, and deposited in the archives at Adelaide Place, London Bridge, for the public service.

(Signed)
J. P. Mather, Chief Clerk.
14 February 1855