Before passing on to the operations of the 'Aurora' during the winter of 1912, I shall briefly refer to the equipment provided for oceanographical work.
The Lucas Automatic Sounding Machine was situated on the port side of the forecastle head. It was suitable for depths up to six thousand fathoms, being fitted with a grooved wheel so as to be driven by a rope belt from a steam-winch or other engine. The wire was wound in by means of a small horizontal steam-engine which had been specially designed for the 'Scotia', of the Scottish Antarctic Expedition (1902) and was kindly lent to us by Dr. W. S. Bruce.
The wire as it is paid out passes over a measuring wheel, the revolutions of which record on a dial the number of fathoms out. A spring brake, which is capable of stopping the reel instantly, is kept out of action by the tension of the wire, but when the sinker strikes the bottom, the loss of tension allows the brake to spring back and stop the reel. The depth can then be read off on the dial.
A hollow iron tube called a driver is attached to a piece of hemp line spliced into the outer end of the sounding wire. This driver bears one or two weights to the bottom and detaches them on striking it; a specimen of the bottom being recovered in the hollow part of the tube which is fitted with valves to prevent water from running through it on the way up. Immediately the driver and weight strike the bottom, the reel automatically stops paying out wire.
To obtain a deep-sea sounding on the 'Aurora', the vessel was stopped, turned so as to bring the wind on the port-bow and kept as nearly stationary as possible; the engines being used to balance any drift of the vessel due to wind or sea.
The difficulties of sounding in the Southern Ocean were much increased by the almost constant, heavy swell. The breaking strain of the wire being only two hundred and forty pounds and the load it had to carry to the bottom weighing nearly fifty-six pounds in air, it could easily be understood that the sudden strain imposed by the violent rolling of the vessel often resulted in the parting of the wire. We soon learnt to handle both vessel and sounding machine in such a way as to entail the least possible strain on the wire.
Of all the operations conducted on board the 'Aurora', deep-sea trawling was the one about which we had most to learn. Dr. W. S. Bruce gave me most valuable advice on the subject before we left England. Later, this was supplemented by a cruise in Australian waters on the 'Endeavour', of the Commonwealth Fisheries Investigation. Here I was able to observe various trawling operations in progress, subsequently applying the information gained to our own requirements on the 'Aurora'.
A short description of our trawling arrangements may be useful to those who are engaged in this work on board a vessel not specially designed for it.
We were provided with three thousand fathoms of tapered steel wire (varying from one and three-quarters to one and a half inches in circumference and weighing roughly a ton to the thousand fathoms in air); this was kept on a large iron reel (A) mounted on standards and controlled by a friction-brake. This reel was situated on the starboard side of the main deck, the wire being wound on to it by means of a chain-drive from the forward cargo-winch.
For heaving in, our steam-windlass was fitted with a specially constructed drum (B), which absorbed the crushing strain and then allowed the slack wire to be wound on the reel (A), which was driven as nearly as possible at the same speed; the windlass usually heaving at the rate of four hundred and fifty fathoms per hour.