Absolute Zero and the Conquest of Cold Read Online Free

likely that inner, narrow transept near the portal through which the king and courtiers would enter, an area they knew would be in shade most of the day and especially at that hour. They also brought in snow, which would have been available from those among the nobility who had on their estates underground snow pits to keep un-melted snow and ice in storage after the winter, to use for cooling drinks in summer. Drebbel filled the troughs and vats partway with water, the coolest he could find, which he no doubt had fetched directly from the nearby Thames. For several hours, he infused nitre, salt, and snow into the water, creating ice crystals and a mixture whose temperature—if he could have measured the temperature, which he could not, since no thermometers capable of such accuracy yet existed—was actually reduced
below
the freezing point of water, as della Porta had guessed. Some of the troughs were metal, and the freezing mixture chilled the metal, which aided the refrigerating process by keeping the contents of the troughs cold.
    More to the point of the exercise, the freezing mixture cooled the air directly above the troughs and vats. In Drebbel's
Elements
treatise he referred to the frequently observed phenomenon of heated air rising, and he seems also to have understood that cool air is heavier than warm air and tends to stay close to the ground. Now he used this principle to generate a mass of cool air that displaced warmer air in the cathedral up in the direction of the capacious ceiling. He did not need to force the warm air to rise very far—just 10 feet high or so, until it was above the height of the king and courtiers. And he did not need to make the space very cold—a decrease in temperature from, say, 85° to 65°F would have proved sufficient to chill an overheated king. This cooling Drebbel accomplished over the course of several hours, perhaps aiding the process by fanning the cool air so that remaining pockets of warm air thoroughly dispersed, before the court party arrived and experienced the shock of the cold.

2. Exploring the Frontiers
    I N THE SEVENTEENTH CENTURY , the capital cities of Europe and England were enlarging in size and population relatively slowly, in part because of society's limited ability to provide food to locations that could not grow enough to feed their own residents. A quarter of the grains, fruits, and vegetables would rot in the fields before being harvested, and eggs and milk would quickly spoil. If the destination of the crops or dairy products was more than a day's wagon ride from the farm, another fraction might become inedible during transport. Evidence that farmers knew that cold retards spoilage comes from their general practice of bringing foodstuffs to the city at night, to take advantage of lower evening temperatures. At city markets, animals used for food were generally killed only after customers had bought them, or no more than a few hours before sale, because uncooked or untreated flesh would not remain edible for long. To hold the live animals, butchers required larger premises than other shopkeepers, which raised the cost of their meat.
    Owing in large measure to the absence of refrigeration, fresh meats, fish, milk, fruits, and vegetables made up a lower percentage of the diet than bread, pickled vegetables, cheeses, and preserved meats. A great deal of ingenuity went into preserving by pickling in salt or sugar, smoking, drying, or excluding air by submerging foods in oil, all of which substantially altered the character and taste of produce or meat. Vegetables and fruits could not be obtained out of season, except at inordinate cost or under special circumstances, as when a king would dispatch a ship to Morocco to bring back oranges in winter.
    In the Temperate Zone, even when ice was available, it was not extensively used for food preservation, the nobility employing their ice facilities mainly to provide chips to cool their wine in