PREFACE 
TO THE 
SEVENTH EDITION. 
issue of this volume appeared, and for some 
time its author has been taken from among us. 
Through six editions his revising oversight was extended 
to the work; and now, when at length it has been 
determined to reissue it under other care, the entire 
aspect of the subject treated of is changed. Im- 
portant facts have been promulgated in the interval, 
which, in this country at least, had been hitherto 
unknown, and novel apparatus and improved methods 
of procedure have taken the place of those of Taylor’s 
day. To express this revolution with faithfulness in 
the following pages, it has been necessary for a very 
large portion of them to be composed of absolutely 
fresh matter. Others, and in fact nearly all, have 
been more or less extensively interpolated and re- 
vised, and altogether the present edition of the 
Manual has in three-fifths of its contents become a 
new book. 
