It depends when exactly you mean by early nineteenth century, as this would change greatly over the next century as telegraphy improves and the technology of trans-oceanic cables are perfected. Most of my information is coming from a class that focused on global communication and therefore telegraphy, so my answer will be focused on that aspect.

My answer draws mainly from the sources provided by my professor:

Communication and Empire: Media, Markets, and Globalization, 1860-1930, by Dwayne Winseck and Robert Pike.

Submarine telegraph cables: Business and politics, 1838-1939 Headrick, Daniel R;Griset, Pascal Business History Review; Autumn 2001; 75, 3; Business Premium Collection pg. 543

Imperial Cable Communications and Strategy, 1870-1914, P. M. Kennedy, The English Historical Review, Vol. 86, No. 341 (Oct., 1971), pp. 728-752

But to get to your question right away, there is a table in her slides that lists the time as 5-8 months to India and another year to get back pre-1840s. With the steamship, this improves to 6 weeks there and 6 weeks back. The telegraph system in 1866 was able to deliver a message in 6 days on average. By 1870, this could be as fast as either 6 hours (Russian route) or 30 hours (Turkish line). By the 1890s it would only take 35 minutes.

There isn't any citation with the table for the pre-telegraphy time and I couldn't find anything referencing that in the sources she gave, but they do detail the development of British communications throughout the nineteenth century. However I did find this article from Siemans that mentions it taking several days.

The development of overseas telegraphy really took off in 1850 with the discovery of gutta percha as an insulator. Gutta percha was a rubbery gum found from the gutta-percha tree in southeast Asia. It would take 3 attempts and until 1866 before a transatlantic cable was successfully lain. The need for a quick line to India was further spurred by the Indian Mutiny of 1857-58 (https://en.wikipedia.org/wiki/Indian_Rebellion_of_1857 ). ( It's kind of hard to read, but a map of the 1858 routes can be found here: http://www.kingscollections.org/exhibitions/specialcollections/imperial-designs/submarine-telegraphy/submarine-telegraphs )

From 1870-onward, the focus of the British Empire was developing "All-Red Routes", that is, entirely traveling through British territories. This is the best picture I could find for showing this territory, dated from 1915. Here's another link depicting some of these routes where you can see their focus on redundancy, especially with the Canada-Australia route. It was a much slower and more expensive route but it served the purpose of added security.

This is my first time answering a question on this sub, I hope it's ok, sorry that it's a bit off-topic. Mods, let me know if there is anything wrong with it or that I should improve upon.

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