During the last years of his life, Professor Morgan had devoted much time and energy to the preparation of a translation of Vitruvius, which he proposed to supplement with a revised text, illustrations, and notes. He had completed the translation, with the exception of the last four chapters of the tenth book, and had discussed, with Professor Warren, the illustrations intended for the first six books of the work; IN THIS IMPORTANT BOOK, the notes had not been arranged or completed. Marcus Vitruvius Pollio (born c. 80–70 BC, died after c. 15 BC) was a Roman writer, architect and engineer, active in the 1st century BC. He is best known as the author of the multi-volume work De Architectura ("On Architecture"). By his own description Vitruvius served as a ballista (artilleryman), the third class of arms in the military offices. He likely served as chief of the ballista (senior officer of artillery) in charge of doctores ballistarum (artillery experts) and libratores who actually operated the machines. After the death of Professor Morgan, in spite of my obvious incompetency from a technical point of view, I undertook, at the request of his family, to complete the translation.