Brilliant_ The Evolution of Artificial Light - Jane Brox [21]
Yet a fourth tower was planned for the reef, this time designed by engineer John Smeaton, who based his plans for it on the shape of an English oak tree, believing that a flared base would give the tower greater stability. The innovative design would be the model for lighthouse construction for more than a century. Smeaton built his light entirely of stone, using granite for the foundation and exterior and softer Portland stone for the interior. Masons in the coastal city of Plymouth began cutting one-ton stones in August 1756, and the following summer they began to build the light. Stevenson wrote:
Fenders fixed on the east side of the Rock prevented boats from fretting against it. Shears and a windlass were fixed for raising the stones directly from a boat and tested by hoisting above the Rock a heavy longboat complete with crew.... Sunday 12 th June saw the first stone, weighing 2 tons fitted in position and bedded with mortar.... Next day the masons set the other 3 stones of the 1st course. On the 15th a heavy swell carried away 5 of the 13 stones ... but the masons at Plymouth working day and night, cut duplicates in 2 days.
They sometimes worked into the summer nights, seeing only by the flickerings of lighted links, or torches, and still it took more than three years to finish the tower, which weighed more than a thousand tons and stood eighty feet above the rocks. First lit in October 1759, the light shining from Smeaton's tower was no different, or stronger, than that in the previous Eddystone lights: a chandelier of twenty-four candles (each about the size of a contemporary dinner-table candle), which the keeper lowered every half-hour for snuffing, then raised again into place. If the glass was clean and the light well snuffed, it could be seen for seven miles: "very strong and bright to the naked eye, much like a star of the fourth magnitude." It stood on the reef for 120 years.
Traffic on the seas increased markedly during the eighteenth century, and the story of the Eddystone light illustrates the lengths to which people would go to achieve even a small glimmer of illumination. They had no hope for more than that, really. In spite of the widespread slaughter of whales, the stink of try-pots, and the complex process of making spermaceti candles, eighteenth-century light wasn't appreciably brighter than what could be had in Roman times, for lamp technology had hardly changed, in part because not even the scientists of the time understood the nature of the flame they were gazing into at night. What would eventually bring about the first measurable increase in the brightness of lamps occurred a world away from the oil-slicked decks of whaling ships, in the laboratories of Europe.
At the time of the French and American revolutions, scientists adhered to the belief that all matter contained phlogiston, a flammable substance that was imparted to the air during combustion. "So long as the air can receive this substance from the combustible matter so long the body will continue burning," noted Professor Samuel Williams, who lectured at Harvard at the time.
As soon as the Air is saturated and can receive no more of the Phlogiston, the combustion must cease for no more Phlogiston can escape or be thrown out from the burning body. And therefore when fresh air is admitted to receive Phlogiston, the combustion will again take place.—And hence are derived the phrases of phlogisticated and dephlogisticated air. By phlogisticated air is intended air which is charged or loaded with Phlogiston, and by dephlogisticated air is meant Air which is free from Phlogiston; or which does not contain this principle or element of inflammability.
Quite a few scientists experimented with combustion in the last quarter of the