xii PREFACE. 



proportioning the power to the effect, are investigations altogether new ; and of 

 necessity so, for the theory of the resistance of fluids hitherto taught in schools 

 is erroneous and cannot be applied. I have therefore endeavoured to explain the 

 methods of my own researches in popular rather than strictly scientific discussions, 

 reserving for a separate work the full developement of my views on this im- 

 portant branch of science. 



The tables will be useful in practice ; and the plates are accompanied by 

 descriptions, so as to render them of easy reference, and also to enable me to 

 refer to the parts of the work which they tend to illustrate. 



I am indebted to the friendly assistance of some of my professional brethren 

 for access to information, which otherwise I could not have obtained : in a few 

 instances their favours arrived too late, except for my own satisfaction in finding 

 that they conformed to the principles laid down in this treatise. Of Mr. Bevan's 

 interesting experiments on the resistance of boats I have given only part, because 

 the others were evidently affected by the limited section of the canal. One of 

 the plates (xm.) was furnished by Mr. White, engineer ; and a few of the others 

 are selected from the very accurate plates drawn by Clement, and published in 

 Partington's ' History of the Steam Engine : ' the rest are engraved from my own 

 drawings, and are aided by a great number of wood engravings on the pages. 



My great object has been to lead the reader to study the principles of the 

 steam engine, and to furnish him not only with materials for study, but also with 

 methods of reasoning, and in sufficient variety to enable him to examine any new 

 case likely to occur ; and in proportion to the care and pains he bestows on the 

 inquiry, he will feel the advantage of the few steps I have taken in this interesting 

 and important subject. 



I shall conclude in the language of Sir Isaac Newton on a greater occasion : 

 " I heartily beg that what I have here done may be read with candour, and that 

 the defects I have been guilty of upon this difficult subject may not be so much 

 reprehended as kindly supplied and investigated by new endeavours of my readers." 



THOMAS TREDGOLD. 



16, GROVE PLACE, 



LISSON GROVE, LONDON. 

 August 13, 1827. 



