PREFACE. 
viii 
London, May, 1844, 
detailed Plates of an engine made in the county. I have, however, not restricted myself 
entirely to an account of this engine, but have taken the opportunity of introducing remarks 
upon the general practice of the county, and have also added in foot notes such other observa 
tions as have seemed to me relevant to the subjects treated of in the text. 
It must be remarked that the general history, description, and principles of action of the 
steam engine are supposed to be previously understood by all readers of this work, which is, 
as appears on its title, a Supplement to a work on the Steam Engine, and does not pretend to 
treat of those principles and facts now so generally known, and to be found in so many 
writings. The matter in this Treatise is therefore limited as much as possible to those parti 
culars of history or description which have especial reference to the Cornish Engine, and 
which, as such, have been either entirely omitted, or very partially treated of in works of a 
more general nature. Our object is to present to engineers and the public generally an 
account of the great and important advances made in the economical improvement of the 
steam engine in that remote corner of our empire alluded to;—advances which have been 
hitherto unequalled and almost unknown in any other part of the world. 
In doing this, I have endeavoured to make prominent the merits of the Cornish engineers, 
particularly those who have distinguished themselves in aiding the course of improvement; 
such as Iiornblower, Trevithick, and Woolf. If it should be thought by any that I have 
passed over with too little notice the advantages resulting from the labours of others, or even 
of the great Watt himself, I would explain that I have deemed it unnecessary in a work of a 
partial nature like the present, to recapitulate what now is become matter of the most widely 
diffused information and the most general knowledge. 
For the purpose of making the work as complete as possible, I have not hesitated to take 
advantage of any matter which I have found already published, and which I have thought 
bearing on the subject. In all such cases I have acknowledged the sources from whence 
I have drawn. 
I have to return thanks to many friends who have aided me in procuring information, and 
among these I would mention particularly Mr. Enys, Sir Charles Lemon, Mr. George Rennie, 
Mr. John Taylor, Messrs. Lean (the reporters of the Cornish engines), Mr. Loam and Mr. 
Sims (Cornish engineers), and Mr. Samuel Hocking, of Hayle. I can also bear testimony, 
from personal experience during my visit to the county in 1841, to the courtesy with which 
strangers are received there, and the willingness of the Cornish engineers to offer to their 
brethren from other parts of the country every opportunity of obtaining information. 
The Two Parts now given form a work complete in itself, as far as the history and description 
of the engine are concerned. It is proposed to add, at a future time, a Third Part, containing 
an analytical investigation of the principles of action of the Cornish Engine, with an explana 
tion of the causes of the increased duty, and general remarks upon the various elements 
which enter into the calculation of the effect of the engine, particularly as regards its economy. 
Examples also will be given in full from engines whose data are known. It was intended for 
this to accompany the present publication, but my sudden departure for India prevented it 
being finished in time. It will form a sequel, and will appear with all possible expedition. 
William Pole.