Good question. The ad doesn't give much context, but given the fact that it's a commercial space, I'm going to assume that it's some kind of mechanical power, probably belt-driven or crankshaft-driven, given the time period and location in a heavily industrialized city.

At the time (and I'm more familiar with the mining aspects of this, given that was the primary use in Alaska), power transfer between an engine and a device was by mechanical means. Take a look at the second image in this BBC slideshow of Burnley, Lancashire.

During the 19th century, Burnley was a global leader in the textile industry, which was an early adopter of powered equipment. The picture shows a massive collection of belt-driven machinery, with people to scale. If you look closely, you'll also see some electric lights hanging from the ceiling, indicating this is a relatively late photograph.

Mechanical drives survive today in your automobile, but by and large they've been replaced by electrical motors in most ordinary applications.