Terraformed Mars in the 19th Century

[Rynn]

I don't know enough about 19th century astronomy to answer whether or not they could see lit up cities however: in 1909 the Meudon 83-inch reflector in Paris was able to get a good enough view of Mars to disprove the Martian canal theory. I'd suggest looking into just how good the telescope was because it could give you a good estimate on whether or not cities would have been visible in the dayside as huge dark growths. I'm fairly certain the answer won't be good however, especially given your requirement that the Martians have Victorian era technology. If the telescope doesn't pan out how about tweaking history a bit further and have Martian radio transmissions intercepted as proof of civilisation?