NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lightning at sea - James Cook - Chain
From: Trevor Kenchington
Date: 2004 Oct 16, 20:24 +0000
From: Trevor Kenchington
Date: 2004 Oct 16, 20:24 +0000
Before anyone draws any comfort at all from 18th-century experiments with lightning chains, it might help to think a bit further about the meaning of "chain". Say the word to most members of this list and I'd guess that the mental image created is one of an anchor chain or at least a chain with oval links like that used for an anchor cable. (Say "chain" to a cyclist and you will create a quite different image in his mind.) So it is worth remembering that Cook most likely never saw, or even heard of, an anchor chain. They did not become standard issue in the RN until around 1811 and would not have been economically viable in Cook's time. "Chain" to Cook, without other context, would probably have meant the rigging chains which linked his ship's deadeyes to her topsides. Those were shaped as oval links (not the flat straps used in the later 19th century) but far more elongated than the links of any anchor chain. However, Cook and the navy in which he served were also very familiar with chain pumps (which had been introduced by 1600), the "chain" of which had far more complex and specialized segments than those of a modern drive chain, let alone those of an anchor chain. A service with that experience which was experimenting with lightning chains would not have been confined to oval links. Given modern knowledge, it could have tried a "chain" made of a series of pieces of iron strap, linked at their ends in the manner of door hinges -- not as effective as an installed continuous copper conductor but able to be stowed below when not in use, protected from corrosion and certainly a far better conductor than any anchor chain. Unfortunately, none of my reference texts on 18th-century ship fittings even mention lightning chains, far less do they illustrate any examples, so I cannot confirm what designs were used. Trevor Kenchington -- Trevor J. Kenchington PhD Gadus@iStar.ca Gadus Associates, Office(902) 889-9250 R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251 Nova Scotia B0J 2L0, CANADA Home (902) 889-3555 Science Serving the Fisheries http://home.istar.ca/~gadus