In the days before the sophisticated mechanical esk calculator and the later electronic devices, d'Ocagne's nomograms were highly regarded methods for performing calculations. This first translation of d'Ocagne's Le Calcul Simplifie makes a classic work on the early art of computation available to historians of computer science.Le Calcul Simplifie, first published in the early 1890s, is volume 11 in the Charles Babbage Institute Reprint Series.