81 The Steamship Savannah

Steamboats on rivers were a success. They easily plied the calm waters. But could they take the battering of a rough ocean? This question was put to the test in 1819. The American packet ship, the Savannah, was planning to steam across the Atlantic. The Savannah was a 110-foot ship. It was not newly built. It was converted. It was a full-rigged sailing ship. It was simply refitted. A steam engine was added to power two side paddle wheels.

The Savannah left New York City on May 22, 1819. It docked at Liverpool, England, on June 20. The journey was made in 29 days. During the trip, the ship ran its engine only 85 hours. After that, the fuel was used up. The rest of the trip was made using sails. The Savannah returned to the United States under sail alone. The engine was not used. Nevertheless, the Savannah is in the records as the first steamship to cross the Atlantic.

Another steamship also crossed the Atlantic, in 1838. It was the British ship, the Sirius. It used steam power all the way. It was also a side-wheeler. The trip took 18½ days.

These trips revealed one serious weakness. It was with the large side-wheels. The waves battered these rather fragile devices mercilessly. Something had to replace them. But what? The solution was the propeller. It was wholly under water at a ship's stern. It used power more efficiently.

The steamship the Great Britain was designed in 1845. It became the first propeller-driven ship to travel across the Atlantic.

81 萨凡纳号蒸汽船

内河蒸汽船很成功，它们在平静的水域中轻松航行。但它们能经受住汹涌大海的冲击吗？这个问题在1819年得到了检验。美国的 packet 船“萨凡纳号”计划横渡大西洋。萨凡纳号是一艘110英尺长的船，它不是新造的，是改装的。它原本是一艘全帆装帆船，只是进行了简单的改装，加装了一台蒸汽机，为两个侧舷明轮提供动力。

萨凡纳号于1819年5月22日离开纽约市，于6月20日停靠在英国利物浦，旅程耗时29天。在航行过程中，这艘船的发动机只运行了85小时，之后燃料耗尽，剩下的航程只能依靠帆船航行。萨凡纳号独自依靠帆船航行返回美国，发动机没有使用。尽管如此，萨凡纳号仍被记录为第一艘横渡大西洋的蒸汽船。

另一艘蒸汽船也在1838年横渡了大西洋，它是英国的“天狼星号”。它全程使用蒸汽动力，也是一艘侧舷明轮船，这次航行耗时18天半。

这些航行揭示了一个严重的缺陷，问题出在大型侧舷明轮上。海浪无情地冲击着这些相当脆弱的装置，必须要有东西来取代它们。但用什么呢？解决方案是螺旋桨，它完全位于船尾的水下，能更高效地利用动力。

“大不列颠号”蒸汽船设计于1845年，它成为第一艘横渡大西洋的螺旋桨驱动船。