From The Company: The Rise and Fall of the Hudson's Bay Empire, by Stephen Bown (Doubleday Canada, 2020), Kindle pp. 46-48:
IT WAS A SEEMINGLY RANDOM flight of fashion that began the dramatic expansion in commerce between the English, French and many of the Indigenous peoples of North America. Furs have always had value in winter for warmth, and to a lesser extent had value for their water-resistant properties, but it was their use in the manufacture of felt that drove the demand in Europe. Felt was developed originally in central Asia as an excellent insulating and waterproofing material for tents and tarps; it was also used in ancient times by Roman legionaries as padding under their armour. In seventeenth-century Europe, felt was primarily used in the manufacture of hats, an ever-changing fashion accoutrement that became an indispensable signifier of prestige and social identity first for gentlemen and ladies and then, as the century progressed, for nearly every status of person. The style of hat signalled the level of prestige and the profession of the wearer. Picture the distinctive tricorne or Continental hat; or the cocked hat of the navy; the dignified stovepipe Regent, or top hat, of the financiers; and the somewhat amusing Paris Beau beloved of the young urban rake. Ladies’ hats had their own hierarchy of frivolity, complexity and expense—and attendant etiquette and social flourishes that governed how a hat was worn and with which accessories, how it was donned and with which distinctive and noble gesture it was removed.
In general, the waterproof and durable beaver felt hat, which could be dyed and moulded into a bewildering variety of shapes, was perfectly suited to symbolize and reflect the desires of an increasingly stratified and mercenary society. People were marked by their hats, the prices of which were well known and appreciated. Since it took about three to four worn beaver pelts to make enough felt for a single hat, some hats were so pricey that they were carefully tended and repaired for years and then passed down as inheritances. Even wealthy people kept inferior spares to be worn in inclement weather, saving their best beaver for notable occasions—or at least occasions when others might note the quality and make of their hat.
Felt was made using heat, moisture, pressure and mercury nitrate to shrink the fur fibres so that they matted together. Hatters spent long hours toiling away in their poorly ventilated tenements, inhaling clouds of mercury fumes as they bent over their felt-making apparatus, combing, pressing and steaming the pelts into the desired consistency and shape. Mercury was eventually discovered to have debilitating effects on the hatter, causing a type of poisoning called erethism, or mad hatter disease, which was characterized by tremors, depression, delirium, memory loss and hallucinations. Hatter wasn’t a profession or trade conducive to a long and healthy life, but nor were many other occupations of the era, and the dangers were poorly understood while the pay could be high.
By the early eighteenth century, London was not only the principal depot for the wholesale warehouses of prime beaver pelts from the best beaver preserve in the world, but by a coincidence of history it was also becoming the global centre for hat manufacture, which for centuries had been based in northern France. Seventeenth-century Europe was riven with religious conflict between Catholics and Protestants. Many of the felt and hat manufacturing trades were dominated by French Protestant Huguenots. In the mid-1680s, they began to flee their homes and cross the English Channel to escape religious persecution. They settled in the vicinity of London and brought with them the secrets of their trade, so that soon the best hats in Europe made from the best beaver pelts from North America originated in London. The most distinguished French nobility, and even Catholic cardinals, ordered their distinctive hats from Protestant hat makers in London.