<Li> The First Transcontinental Railroad in the USA is completed in 1869 . </Li> <Li> The Suez Canal in Egypt is opened in 1869 . </Li> <Li> The Plongeur, the first mechanically powered submarine in the world, is launched in 1863 after three years of construction . </Li> <Li> Carl Wilhelm Borchardt discovers and proves Cayley's formula in graph theory in 1860 . </Li>

What was happening in 1860 in the world