Ever since boats first ventured into deep water, sailors have needed anchors. At first, an anchor was simply a stone on the end of a rope. Of course, it helps if you can drill a hole through the stone to tie the rope to, though I’m sure the earliest anchors did not have such a refinement.
This is just such an anchor (a Public Domain image from Wikimedia), found in the ruins of the ancient city of Byblos in Lebanon. Something similar is still sold, usually under the name mushroom anchor, made out of cast iron or cast lead, and often coated with plastic.
But this kind of anchor is not very efficient. Early sailors figured out that they could make a much more efficient anchor. An efficient anchor need these characteristics:
- It must be heavy enough to sink to the bottom of the sea.
- It must have a tool for digging into the sea bottom.
- It must have some way of ensuring that the anchor always comes to rest on the sea floor in a position such that the tool actually digs into the sea floor when the boat pulls on the anchor line.
This image (Photo by Bukvoed) is an ancient anchor from Askelon, Israel. The brown parts are wood, and the grey parts are lead. The lead has two functions: to make the anchor heavy, and to provide strength and shape to the places where it is used. In this anchor, the piece of lead on the left forms the stock, which has the primary purpose of ensuring that the either one of the arms (the sharpened wooden points) faces into the sea bed so that it will dig in when the boat pulls on the rope that forms the anchor line. The stock for an anchor such as this has to be heavy enough to sink this end of the anchor to the sea floor, long enough to ensure that it lies flat, and strong enough to ensure that it does not bend, even when the anchor drags. Each arm has to be strong enough to stop any drag the boat might put on the anchor line, and long enough to dig into the sea floor deeply enough to stop the anchor from dragging. The wooden beam connecting the stock to the arms is called the shank. It has to be long enough to ensure that the weight of the stock tips the anchor onto its side, as shown in the picture, even when the sea floor is uneven. The dimensions and proportions of an anchor must have been determined over many years by trial and error.
The anchor shown possibly dates back to pre-Roman times (more than 2000 years ago), but the wooden parts are most likely a modern reconstruction.
By the time of the Roman Emperor Caligula (37-41 AD), some anchors were made of iron, but lead stocks were also still used.
This anchor was recovered from the wreckage of a ship in Lake Nemi, Italy, built for Caligula. It has a lead stock, wooden shank, and wooden arms, but the wooden parts (oak) are reinforced with iron bands, and the points of the arms are iron. The wreckage was well preserved, and the wood in this anchor is original.
The frieze on Trajan’s Column in Rome (113 AD) shows a similar anchor:
Anchors for the following 1900 years were dominantly this same general shape: two symmetrical arms to dig into the sea floor, a stock at right angles to the arms, and a long shank connecting the arms to the stock.
An interesting discussion of the development of anchors is given in a paper by Gerhard Kapitän, Ancient anchors–technology and classification, published in The International Journal of Nautical Archaeology and Underwater Exploration (1984)13.1:33-4
I’ll talk about modern anchors in another post.