This image of the mill hammer type thats used in Dowlais Ironworks in the nineteenth century, is taken from http://www.archive.org/details/ironmanuf00trurrich
digitized by the Internet Archive in 2007 with funding from Microsoft Corporation
'The iron manufacture of Great Britain theoretically and practically considered' by W. Truran 2ndedition, 1862. More information on the individually numbered parts can be found there, in the index of plates at the end of the contents pages.