Digging deeper > How to power trains underground
Without ventilation, it was impossible to use steam trains in deep underground tunnels. Various alternatives were tried before the 1880s. Air under pressure could be used to produce pneumatic power, but this was never successful on a full-scale railway.
When the first Tube railway was constructed, the company planned to run the cable system already successfully used overground in San Francisco, pioneered by Siemens. In the end, they chose electricity, a new high-risk technology.