It's a cool resource for a writer, and just generally a neat site to explore.
" The population of London is nearly doublethat of Paris, four times that of New York, five times that of Berlin, six timesthat of St. Petersburg, twelve times that of Amsterdam, and eighteen times thatof Rome. The inhabitants of Paris, Berlin, Vienna, and St. Petersburg, addedtogether, fall short of the population of London, which exceeds that of allScotland, is more than equal to two-thirds of the population of all Ireland, andconstitutes nearly one-eighth of the whole population of Great Britain. Theincrease alone in the inhabitants of London during the last thirty years,exceeds the entire population of the kingdom of Greece, brigands included."
(Link thanks to Boing Boing)