Frederick Douglass in a moving essay writes:
I afterward got steady work at the brass-foundry owned by Mr. Richmond. My duty here was to blow the bellows, swing the crane, and empty the flasks in which castings were made; and at times this was hot and heavy work. The articles produced here were mostly for ship work, and in the busy season the foundry was in operation night and day. I have often worked two nights and every working day of the week. My foreman, Mr. Cobb, was a good man, and more than once protected me from abuse that one or more of the hands was disposed to throw upon me. While in this situation I had little time for mental improvement. Hard work, night and day, over a furnace hot enough to keep the metal running like water, was more favorable to action than thought; yet here I often nailed a newspaper to the post near my bellows, and read while I was performing the up and down motion of the heavy beam by which the bellows was inflated and discharged. It was the pursuit of knowledge under difficulties, and I look back to it now, after so many years, with some complacency and a little wonder that I could have been so earnest and persevering in any pursuit other than for my daily bread. I certainly saw nothing in the conduct of those around to inspire me with such interest: they were all devoted exclusively to what their hands found to do. I am glad to be able to say that, during my engagement in this foundry, no complaint was ever made against me that I did not do my work, and do it well. The bellows which I worked by main strength was, after I left, moved by a steam-engine.
More here.