My first novel, State of Treason was half written when my writing veered away from its planned structure and took off in an unexpected direction. More than a minor diversion, I had to halt writing and research the background to this new sub-plot. I shouldn’t have been surprised. The book was an Elizabethan thriller set in 1578; a time when English privateers and merchants were planning and undertaking great adventures to the New Lands and raiding Spanish treasure ships. For reasons that I won’t divulge here, my fictitious protagonist, scholar and physician William Constable, is caught up in the preparation for one such venture.
The financier for the venture was a wealthy merchant, while the leaders were real historical figures, John Hawkins and Humphrey Gilbert. Hawkins was an adventurer, ship’s captain and ultimately an Admiral who was second in command in the battle against the Spanish Armada. He is known as one of the first slave traders and a pioneer of ‘triangular trade’. This involved capturing or buying slaves in West Africa, sailing across the Atlantic to Spanish settlements and trading slaves for sugar and molasses, which were then sold back in Europe at great profit. Hawkins was also inventive as a ship builder and it was largely down to him that the English navy built fast, efficient galleons. The overall impression I gathered of Hawkins was of a brave and intelligent man, but not an endearing one.
Sir Humphrey Gilbert was an adventurer, explorer, member of parliament and soldier. He was noted for his cruelty during a military career in Ireland and courage as a pioneer of the English colonial empire in North America. The historian A L Rowse described him as having, ‘… a questing and original mind, with the personal magnetism that went with it. People were apt to be both attracted and repelled by him, to follow his leadership and yet be mistrustful of him.’
Elizabethan adventurers were certainly brave. The ships they sailed were small, navigation was uncertain, but potential rewards were enormous. In 1578 Francis Drake was in the Pacific, mid-way into his circumnavigation, returning to Plymouth in 1980. The Queen’s half share of Drake’s treasure was more than enough to pay off the entire national debt. No wonder Drake got a knighthood.
A major part of my new research entailed a crash course on celestial navigation. I created William Constable as a mathematician and surveyor of the movement of the stars. In the past, he had worked on ways to improve navigation. The adventure, led by Hawkins and Gilbert, rekindles his interest, and in order to gain their confidence, William invents a way to measure latitude with improved accuracy. He names his new device a “shadow staff”.
The art of navigation developed rapidly in the sixteenth century in response to explorers who needed to find their positions without landmarks. Instruments were used to determine latitude, but longitude required accurate timepieces and these were not yet available. Instead, navigators used educated guesswork or ‘dead reckoning’ by measuring the heading and speed of the ship, the speeds of the ocean currents and drift of the ship, and the time spent on each heading.
A cross staff was in common use in the mid sixteenth century as an instrument to calculate latitude. This device resembled a Christian cross. The vertical piece, the transom or limb, slides along the staff so that the sun or star can be sighted over the upper edge of the transom while the horizon is aligned with the bottom edge. The major problem with the cross-staff was that the observer had to look in two directions at once – along the bottom of the transom to the horizon and along the top of the transom to the sun or the star. No mean feat on a rolling deck.
A more advanced instrument was the Davis Quadrant or backstaff. The observer determined the altitude of the sun by observing its shadow while simultaneously sighting the horizon. Captain John Davis conceived this instrument during his voyage to search for the Northwest Passage and is described in his book Seaman’s Secrets, 1594. One of the major advantages of the backstaff over the cross-staff was that the navigator had to look in only one direction to take the sight – through the slit in the horizon vane to the horizon while simultaneously aligning the shadow of the shadow vane with the slit in the horizon vane.
The shadow staff in the book, invented by William Constable, is an imagined forerunner of the backstaff.
By Paul Walker