Harriet Beecher Stowe's influential novel Uncle Tom's Cabin became an overnight success when it was published in 1851, stirring up a great deal of public feeling against slavery. Mrs Stowe was 40 years old at the time; indeed today, June 14th, is the 190th anniversary of her birth in 1811.
This powerful, melodramatic tale is primarily concerned with the misadventures of the ill-fated Uncle Tom. But for many of us the story is chiefly memorable for Eliza's dramatic escape to freedom from Kentucky across the ice on the almost frozen Ohio River: "She caught her child, and sprang down the steps towards the river. With one wild cry and flying leap, she vaulted sheer over the turbid current by the shore, on to the raft of ice beyond."
Now in some ways Stowe paints an unfamiliar picture. "It was now early spring," she writes, "and the river was swollen and turbulent; great cakes of floating ice were swinging heavily to-and-fro in the turbid waters. The ice had been lodged and detained in great quantities, and the narrow channel which swept round the bend was full of ice, piled one cake over another." But it is unlikely that we would see so much ice on the Ohio nowadays. There are several reasons why rivers in the temperate latitudes of the northern hemisphere are more reluctant to freeze than they were in the first half of the 19th century.
For one thing it is warmer. Since about 1850 the average temperature of the northern hemisphere has been rising steadily, and is now one full degree Celsius higher than it was in the chilly early 1800s. Secondly, the river-banks are more populated, with large cities dotted along their length; some of the heat generated by the extra people inevitably finds its way into the rivers, decreasing their likelihood of freezing. And thirdly, the rivers flowed largely though a countryside in its natural state, much of it part wood, part marsh, and almost wholly undrained; they meandered over their flood plains, often flowing more slowly and therefore freezing more easily than swiftly running streams.
Be that as it may, there was certainly ice on the Ohio when Eliza was obliged to flee. "The huge green fragment of ice on which she alighted pitched and creaked as her weight came on it, but she stayed there not a moment. With wild cries and desperate energy she leaped to another and still another cake - stumbling - leaping - slipping - springing upwards again! She saw nothing, felt nothing, till dimly, as in a dream, she saw the Ohio side, and a man helping her up the bank."