When Every Thumb was a Marlinespike
The Longwinded Shantyman
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?
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
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