INTRODUCTION. 
XXXVIT 
Dr. Barnard, who, in addition to bis knowledge of natural history, pos- 
sesses mechanical ingenuity of a high order. After giving some time 
to general observations in Mississippi and Alabama in the summer of 
1880, he was called to Selma the latter part of August, and charged 
with mechanical work. It was there and early in September that 
the cyclone-nozzle originated in our endeavors to contrive something that 
would throw a spray from the ground up. The question was dis- 
cussed between us as to whether water forced tangentially into a flat- 
ened disc would rotate and issue from an outlet in a straight or in a 
spreading jet. Dr. Barnard took the latter view, and a disc, improvised 
by means of two watch crystals, so as to permit the motion of the liquid 
to be seen, proved that he was correct. The size and form filially 
adopted is the result of numberless subsequent experiments covering 
a period of nearly two years. 
While we have always had a number of original ideas to carry out 
and our direction of this work has been active, yet Dr. Barnard's as- 
sistance was fertile from the first, and there is so much that has resulted 
therefrom that the preparation of these chapters was finally assigned 
to him, and he deserves much of the credit that attaches to them. It 
was found expedient, on account of the large increase of matter, to de- 
par? l'rom the general arrangement adopted in the first edition, which, 
while it had the merit of simplicity, did not permit of so thorough a 
classification. Much of the material in that first edition, is, however, 
used verbatim in these chapters ami such is placed in quotation marks, 
60 that any quoted passage without authority or credit may be under- 
stood as being from that edition. 
In describing these various machines and contrivances, it has been the 
endeavor to bring to the notice of the planter all that are worthy of 
mention, and to point out their advantages and disadvantages and how 
they may be used most economically and eilectively. The planter can 
then judge for himself which he can most profitably adopt according 
as his own circumstances dictate. Many of the older machines and 
contrivances are thus mentioned or described (though now superseded 
by improved ones) because they are of interest from a historical point of 
view. 
Chapter XIV gives a short account of the history of the literature 
on the Cotton Worm and closes with ;i bibliography up to and including 
the year 1881. 
In Chapter XV are illustrated and described some of those insects 
which either in the larva state, but more particularly in the imago state, 
are liable to be confounded, and in fact have often been confounded, 
with the true Cotton Worm. As the northern Army Worm (Leucania 
nnipuncta) in the imago state is, from its color and frequency, most 
often thus mistaken in winter time, we have introduced a colored plate 
of the species to facilitate comparison. 
Chapter XVI is devoted to the Boll Worm, and will be found to con- 
