Relationships Between Ideas

Why the Thames Froze

Between 1309 and 1814 the Thames froze hard enough to walk on at least twenty-four times. Since 1814 it has not once. The usual explanation is that the climate has warmed. That is part of it, and not most of it. Old London Bridge had nineteen arches on wide stone piers. The piers took up so much of the channel that the bridge acted as a weir, slowing the water upstream almost to a standstill. Still water freezes; moving water does not. The river was also shallower and wider then, spreading over land that has since been embanked. Shallow water loses heat faster. Old London Bridge was demolished in 1831. The embankments were built between 1862 and 1874. The river that flows through London now is narrower, deeper and faster than the one that froze — and it would not freeze in a colder winter than any of those.

Two Plants, Two Histories

Tea and coffee are both leaves or seeds steeped in hot water, and both became national habits. How they got there could hardly be more different. Tea came to Britain through a monopoly. The East India Company controlled the trade for nearly two centuries, and the government taxed it so heavily that by the 1770s most tea drunk in Britain had been smuggled. When the tax was cut in 1784, smuggling collapsed almost overnight. Coffee spread through places rather than trade. The coffee house arrived in Britain in the 1650s and became somewhere to read newspapers and argue. Lloyd's of London and the London Stock Exchange both began in one. Tea won the home; coffee won the meeting. Neither plant grows in Britain. Both habits are entirely imported, and both are now so ordinary that they are thought of as native.