The Right Chemistry: Montreal has its very own ‘shot tower’

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The structures were designed to manufacture “shot,” lead pellets fired from shotguns. None remain active; other technologies are now used.

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Education sometimes takes a circuitous route. Like my learning about the fascinating history of “shot towers.” Appropriately enough, it all began with Sherlock Holmes, investigator extraordinaire. I was trying to track down Sidney Paget’s original illustrations as they appeared in the story of The Red-Headed League, published in the Strand magazine in 1891. As one might expect, a reproduction of the issue wasn’t difficult to find online, replete with Paget’s wonderful drawings. Glancing at the last page of the Holmes story, my eye caught the next article in the magazine, titled Up the Shot Tower, which was accompanied by a picture of a building that looked something like a lighthouse. And thus began a journey through history that would end with an awe-filled upward gaze on Dominion St. in Montreal.

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“Shot Tower” turns out to be appropriately named, given that the structure is designed to manufacture “shot,” tiny lead pellets fired from shotguns. That requires gunpowder, a mixture of sulphur, charcoal, and saltpetre (potassium nitrate) first described in China in the ninth century. It was likely an accidental byproduct of experiments seeking to find the “elixir of life,” as suggested by the Chinese name given to the substance that translates as “fire medicine.” By the 12th century, the Chinese had developed “fire lances,” essentially bamboo tubes packed with gunpowder that would forcefully eject arrows or bits of metal upon ignition.

Before long, Chinese metalworkers developed real cannons cast of brass or iron, and by the 14th century, the technology had landed in Europe with craftsmen designing “hand cannons.” These, loaded with lead pellets, were the forerunners of all guns. The use of lead was already well established, with the smelting of the metal’s ore, galena (lead sulphide), dating back to around 6000 BC. Lead is easy to cast and shape, a property with which the Romans were very familiar. They famously constructed water pipes and made dining vessels from lead, oblivious to the metal’s toxicity. But pouring lead into wooden molds to make “shot” in the amounts required for weapons was an inefficient process. Then in 1782 came the breakthrough. The shot tower!

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English plumber William Watts gets credit for the discovery. As a plumber, he knew all about working with lead. Indeed, the name of the profession derives from “plumbum,” the Roman term for the metal, which also explains why Pb is the chemical symbol for the element.

There are a number of stories circulating about how Watts hit upon the idea of a shot tower. According to one, after a day’s work of casting lead for shot, he imbibed of ale a bit too freely, fell asleep, and had a dream in which rain turned to lead, covering the wet ground with tiny pellets. Intrigued by this vision, he melted some lead and dropped bits from different heights, noting that the drops became rounded as they fell. Another account suggests that Watts knew that castles were sometimes defended by pouring molten lead on the enemy, with the metal ending up in the moat from which it was recovered in the shape of balls. The most likely explanation, though, for sparking the idea of a shot tower is Watts’s observation that as a drop of water falls from a faucet, its shape changes from a teardrop to a sphere. Perhaps drops of lead would do the same!

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But how do you keep the molten droplets from splattering when they hit the floor? How about allowing them to fall into cold water? Height turned out to be an issue with drops of lead having to fall a greater distance than drops of water to achieve a spherical shape. First, Watts knocked out a hole in the ceiling so he could drop the lead from the second floor of his house, undoubtedly to the dismay of Mrs. Watts. When this wasn’t high enough, he added stories until the house became a tower. Pouring molten lead from the top through a copper sieve now resulted in perfect shot being recovered from the tub of water placed at the bottom.

Watts’s “shot” was soon heard around the world and “shot towers” began to sprout up everywhere. One of these was on the banks of the Thames in London, as described by the author of the article I had come across in the Strand. That tower had 327 steps and produced a silvery rain of millions of pellets every day. The first tower in America, Philadelphia’s “Sparks Tower,” was built in 1808 and produced tons of ammunition during the War of 1812 and the U.S. Civil War. At 234 feet, Baltimore’s “Phoenix Shot Tower,” dating back to 1828, was the tallest structure in the United States until the Washington Monument was completed in 1884.

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A number of shot towers can still be found around the world, although none are active, the technology having been replaced by modern machinery. Unfortunately, both Watts’s original and the London tower that set me on my journey are gone, as I discovered when searching for still existing towers. But it was during that search that I suddenly gasped when I came across a mention of Montreal. I was astounded to discover that we have a shot tower right here. Of course I had to go see it.

The Stelco Tower looks to be about 10 storeys high and can be found on Dominion Street, right by the Lachine Canal, just east of the Atwater Market. I must have seen it numerous times as I bicycled along the canal, but never noted it. Now I gawk at this wonderful historic relic every time, as will you if you have a chance to wander that way.

And there you have the shot tower story, lock, stock and barrel! Thanks, Sherlock.

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Joe Schwarcz is director of McGill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.

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