I am a locomotive engine. I work hard day and night, and earn my living. I take great

I am a locomotive engine. I work hard day and night, and earn my living. I take great loads up steep gradients, and I bring down bigger loads still. I am strong, and I can pull. I can pull heavy guns, and I can pull cheques. I can pull passengers and parcels, and I can pull profits. I can pull all sorts of things, from a pig to a palace. In short, I am a locomotive engine.