Read the passage from Sugar Changed the World.A stream of pale ash-colored syrup gushed out from the mills, bubbling white with foam. The liquid rushed down a wooden gutter directly into the boiling house, a building of massive furnaces and cauldrons, where the syrup was heated and strained and turned into crystals. A giant copper kettle—often about four feet across and three feet deep—waited for the pale river. This was the first in a series of ever-smaller cauldrons, and beneath each gaped what the Brazilians called the "great open mouths"—the huge furnaces that had to be constantly filled with the wood that workers had chopped down and hauled to be ready for this moment. The boiling house was as perilous as the mills, for if a person nodded off for a second, he or she could slip into a bubbling vat.Mammoth fires burned in the "mouths," clouds of steam billowed above the kettles, and the heat was so intense that the boiling houses had to be sprayed with water so they would not go up in flames. Then there was the smell, or rather, the stench of the boiling liquid. As the [sugar cane] juice boiled, a foul scum rose to the top—which a slave had to keep skimming off with a long-handled ladle. Over and over again the liquid had to be strained and purified, even as it kept boiling, boiling, boiling in the copper vats.