Barddas, a collection of original documents illustrative of the theology, wisdom and usages of the Bardo-Druidic system of the Isle of Britain was published in English in 1862. An incomplete second volume was found after the death of the translator and published in 1874. Both volumes are included in this book, which has the Welsh and English on facing pages for the convenience of scholars who may wish to test the accuracy of the translation by reference to the original. In Wales there has existed for a considerable time a body of teaching purporting to contain a portion, at any rate, of that ancient Druidic thought which, as Caesar tells us, was communicated only to the initiated, and never written down. This teaching is principally to be found in Barddas, a compilation made from materials in his possession by a Welsh bard and scholar named Llewellyn Sion, of Glamorgan, towards the end of the sixteenth century, and edited, with a translation by J. A. Williams ap Ithel for the Welsh MS. Society.