Human Computers

Human computers were slow at computing, and they didn't like computing. Moreover, human computers were prone to making errors. And, worse, because the calculation tables in one book would often be employed in creating a new set of computations in another, these errors would infect other computations, rendering them erroneous as well. By the 1800s, the situation was literally disastrous: the sets of computation books available were so riddled with errors that, for example, ships were running aground due to errors in navigational computations. (Compare this situation with the present-day importance of onboard computers to air and space travel: navigation requires enormous amounts of computation).