I simply said that something had to replace horses in large cities. Things that replaced them included trains and subways (powered by steam and later electricity), cable cars, buses, trucks, cars, etc. Yes, there were trains and cable cars and subways before the horses were eliminated.
http://www.apta.com/...tory/mileston.cfm
But it wasn't until electric trains and gasoline and diesel powered vehicles took off that horses became much less popular in cities.
A modern city cannot function with draft animals providing most of the power. Some type of machine had to replace them.
Cheers,
Scott.