Nasmyth thought the matter over and seeing the obvious defects of the tilt-hammer (it delivered every blow with the same force) sketched out his idea for the first steam hammer. He kept his ideas for new devices, mostly in drawings, in a "Scheme Book" which he freely showed to his foreign customers. Nasmyth made a sketch of his steam hammer design dated 24 November 1839, but the immediate need disappeared when the practicality of screw propellers was demonstrated and the "Great Britain" was converted to that design.