four-fifths of the steam power used to blow their furnaces
actually cools them.

I have collected, with some pains, the criticisms* on the
first edition of this work, and have availed myself of much
information which has been communicated to me by my friends, for
the improvement of the present volume. If I have succeeded in
expressing that I had to explain with perspicuity, I am aware
that much of this clearness is due to my friend, Dr Fitton, to
whom both the present and the former edition are indebted for
such an examination and correction, as an author himself has very
rarely the power to bestow.


[*Footnote: Several of these have probably escaped me, and I shall
feel indebted to any one who will inform my publisher of any future
remarks.]


22 November, 1832.




Section I.




INTRODUCTION.