A Description of the Admirable Table of Logarithmes is said to be the book that freed the world from a logjam of calculations. John Napier spent more than twenty years working alone on his sytem of logarithms, during a time when the multiplication and division of large numbers, as well as the finding of square roots, was considered to be extremely difficult. Because of his discovery of logarithms, these tedious mathematical operations could be replaced by the much easier processes of simple addition, subtraction and division by two. Never again would astronomers, architects, merchants and navigators become bogged down with calculations that were simply too difficult or time consuming to carry out. The French mathematician and astronomer Pierre Simon Laplace said that logarithms, '...by shortening the labours, doubled the life of the astronomer.'