The racial division of the 'White Town' and 'Black Town' was replicated by dividing Calcutta on what grounds by the Britishers in the 19th century?

Healthy and Unhealthy

By the late nineteenth century, official intervention in the city became more stringent. Gone were the days when town planning was seen as a task
to be shared by inhabitants and the government. Instead, the government took over all the initiatives for town planning including funding. This opportunity was used to clear more huts and develop the portions of the town.
at the expense of the other areas. The existing racial divide of the 'White town' and the 'Balck town' was reinforced by the new division between the 'healthy' and 'unhealthy'.