First edition, first printing. 96pp, with 16 black and white plate illustrations and further drawings in text. In grey cloth-covered boards with brown titles front and spine. Illustrated endpapers. 8vo. Cloth a little marked, gently pushed at spine tips. An introductory of how hydro-electric power works, with chapters including features on Niagara, the St Lawrence Power Project and hydro-electric power in Britain.
