PREFACE. vil 



courtesy of the Royal Society, Institution of Civil Engineers, 

 Institution of Mechanical Engineers, Society of Arts, British 

 Association, Society of Telegraph Engineers, Iron and Steel 

 Institute, Royal Institution of British Architects, Institute 

 of Naval Architects, Physical Society, Royal United Service 

 Institution, Royal Institution, Chemical Society, Society of 

 Chemical Industry, who most generously placed their trans- 

 actions and blocks at the disposal of the Executors, for which 

 they beg also to express their cordial thanks. 



THE EXECUTORS. 



