Opus number developed other catalogue-number systems; among them the "Bach-Werke-Verzeichnis" (BWV-number), and the "Köchel-Verzeichnis" (K- and KV -numbers) with which are organised the works of Johann Sebastian Bach and Wolfgang Amadeus Mozart, respectively. In the classical period, the Latin word "opus" ("work", "labour") was used to identify, list, and catalogue a work of art. By the 15th and 16th centuries, the word "opus" was used by Italian composers to denote a specific musical composition, and by German composers for collections of music. In compositional practise, numbering musical works in chronological order dates from 17th century Italy, especially Venice. In common usage, the
19th-century London and other kiln-fired tiles became popular facings for buildings in the 1880's and 1890's, because they resisted soot and damp and also provided much-welcome color to buildings that were otherwise drab. Many famous buildings and landmarks of London were constructed during the 19th century including: 19th-century London This article covers the 19th century history of London, during which it grew enormously to become a global city of immense importance, and the capital of the British Empire, fed by immigrants from the colonies and refugees from conflicts and famines. It was the largest city in the world from about 1825, the