Following its introduction to Queen Victoria at the Great Exhibition in 1851, the stereoscope quickly became a popular entertainment tool in the homes of middle-class Victorians. A three-dimensional effect was created when two identical photographs were mounted on a slide and viewed through an optical device. Seen as a means of exploring the wider world, common images produced for the stereoscope included scenes of landscapes, monuments and foreign lands. Like the stereoscope, the steamship was a technological wonder of the Victorian age. Although steamships operated as mail couriers in the British Isles from the 1820s, they were initially employed in Southeast Asian waters as military vessels in naval operations against indigenous pirate vessels due to their high operational costs. It was only in 1845 that a dedicated mail steamer route covering Ceylon, Penang, Singapore and Hong Kong at monthly intervals was put into operation by the British-owned Peninsular and Oriental Steam Navigation Company (more commonly known as P&O).