There's also a wonderful book called "Weather prediction by numerical process" by Lewis Fry Richardson, published in, IIRC, the 1920s. In it he explains how to predict the weather using methods similar to what we use now, the significant difference being that instead of handing the data to a computer, he would hand it to a vast amphitheatre full of people, all of them trained to perform particular mathematical operations accurately, who would pass their results one to the other until all the data was crunched. His "computers" even had a clock signal just like ours - a conductor standing where they could all see him.