Saturday, July 21, 2012

Echo's Voice

When Every Thumb was a Marlinespike

The Longwinded Shantyman

A Spontaneous Song Circle.
Copyright 2012 by Cheryl Jones

     My dog Echo’s first experience with a crab was when one latched onto her upper lip after her inquisitive nose brought it within range of the crustacean’s snapping pincers. Echo’s frantic barking alerted me to her predicament. The sight of the crab bobbing with the rhythm of her baying was made even more hilarious by the repeat of Echo’s indignant yelping echoing off the cliffs bordering the opposite shore. The silly girl thought the sound was another dog, and split her attention between barking at the distant hound mocking her and the evil red rock that had reared up and bit her.

      What was a great laugh then was actually quite instructive when you stop to think about it. What if Echo’s situation had occurred during the age of sail? What if it had been fully dark out? Or foggy? What could Echo’s voice have accomplished for a mariner of old? Back then, the demise of most ships wasn’t the sea, it was the shore. A sailing instructor I once trained under was fond of saying, “Rocks are hard, water is wet, and the wind will blow where it will”. With those three truths in mind we can begin to form a picture of what the past sailors had to contend with in order to keep their vessels afloat. A traditional sailing ship didn’t have radar, or a spotlight, so what to do to pierce the gloom? Many tricks were employed, but the most common was to use echo’s voice to literally hear the distant shore.

Sonic Ranging in the Age of Sail

      In dry air, sound travels approximately one mile every five seconds. With that in mind, if a loud enough noise was created aboard a fogbound vessel that lay two miles from a rocky shore, the resulting sound waves would radiate outward, echoing off the danger ten seconds later, and then arrive back at the ship ten seconds after that. A navigator hearing an echo after twenty seconds, even if blindfolded would say, “The shore is two miles away.” But how could that sailor first produce a sound loud enough to remain audible for more than a quarter of a minute on a foggy night?

Firing blanks from the privateer Lynx's carronades.
Copyright 2012 Cheryl Jonesion

      It is an interesting historical fact that cannons and swivel guns were used for navigational sonic ranging more often than they were for hostilities. There was no need to expend shot. The gunner would fire a blank charge; just as the sail training vessels do now during mock battles. The shape of the echo would tell a great deal about the invisible object. Imagine the audible difference between a tree-lined shore, a sheer cliff, and a rugged mountain. All produce different reflections - and a sweeping shoreline produced them at different intervals. This proved a highly accurate method of gathering navigational data and is how the original charts of Puget Sound were created. If a vessel were close enough to the object of concern/interest then there was no need to expend black powder. A found object, such as a conch shell, could trumpet a cry loud enough to produce the necessary echo. In closer quarters hand clapping and even human voice were resorted to.

      In modern times I have tried all of these methods and found that they work astonishingly well. You can try it for yourself. Go from room to room in your house and in each close your eyes and clap your hands. Listen to the different size of each room - the hard, bright walls in the bathroom and kitchen, the soft quiet of the bedroom. Watch and listen intently during the next thunderstorm, or better yet, the next time you are boating close your eyes and sing a shanty. Perhaps a voice will join you from far away - echo’s voice. Perhaps that is what the sailors of old heard singing back from the rocks, and in their desperate loneliness spun the tales of the sirens. 

Mark Olson