I am a locomotive engine. I run upon rails from place to place, and I carry burdens u

I am a locomotive engine. I run upon rails from place to place, and I carry burdens upon my back. The weight of me alone is great, but the weight I carry is greater. I can draw a load after me, to the extent of many tons; and I can draw it fast and far. I am strong, and my strength is great. I can draw up a steep hillside, and I can draw down into a deep valley. Sometimes I am made to