"All that Napier has left us on the subject of logarithms is contained in two short books, the one known as the Descriptio, published in 1614, and the other known as the Constructio, published after his death in 1619. Internal evidence as well as the distinct statement of his son, who published the Constructio, make it clear that it was in fact written many years before the Descriptio, and it represents in many passages an earlier stratum of thought. ...Napier saw and approved of a translation into English of the Descriptio, and about twenty-five years ago an excellent translation of the Constructio was published in Edinburgh."