“Using a prism allows me to see the sun in a different light.”
Portland cementIn 1824, in Yorkshire, England, Joseph Aspdin, a stone mason, patented Portland cement, made by burning finely pulverized lime and clay at high temperatures in kilns (UK patent No. 5022). Thus Aspdin had made a manufactured counterpart to natural or Roman cement - a crude formulation of lime and volcanic ash used as early as 27 BC. Aspdin produced a hydraulic cement that would harden with the addition of water. He named his invention "Portland cement" not only to distinguish it from Roman cement, but also as a marketing tool: concrete made from his new cement resembled a highly prized building stone quarried on the Isle of Portland off the British coast. Like flour in a fruit cake, cement glues aggregate (sand or gravel) together to make a "rock" (concrete). |
