iv PREFACE. 
Including this time, they are the result of 
fourteen years’ close attention to a subject 
which always had a peculiar interest with the 
author. 
There being no text-book or guide on the 
subject, so far as the author is aware, he feels 
that, though no longer in the profession, he 
has contracted an obligation to impart to others 
that which dearly-bought experience has taught 
him; and his end will have been answered if, 
with the help of these pages, young practi- 
tioners learn the subject at an easier rate 
than he did. 
It is also humbly hoped that these pages 
may be of some use to those whose years and 
maturity have secured them that confidence in 
their skill which is the laudable ambition of all. 
W. F. 
Lonpon, Ist Fan., 1878. 
