to those unfamiliar with recent researches in this field.

It is well known that in coal-tar is found a series of ammonia-like
bases, aniline or amido-benzol, toluidine or amido-toluol, and xylidine
or amido-xylol, which are utilized practically in the manufacture of the
so-called aniline dye-colors. It is perhaps not so well known that there
are other series of bases found there too. The first of these is the
pyridine series, including _pyridine_, C_{5}H_{5}N, _picoline_
(methyl-pyridine), C_{5}H_{4}N(CH_{3}), _lutidine_ (dimethyl-pyridine),
C_{5}H_{5}N(CH_{3})_{2}, and _collidine_ (trimethyl-pyridine),
C_{5}H_{2}N(CH_{3})_{3}. This series is also found in relatively larger
proportion in what is known as Dippel's oil, the product of the dry
distillation of bones.

The second series is the quinoline series, including _quinoline_,
C_{9}H_{7}N, _lepidine_ (methyl-quinoline), C_{10}H_{9}N, and
_cryptidine_ (dimethyl-quinoline), C_{11}H_{11}N. The two compounds
which give name to these series, pyridine, C_{5}H_{5}N, and quinoline,
C_{9}H_{7}N, respectively, bear to each other a relation analogous to
that existing between benzol, C_{6}H_{6}, and naphthalene, C_{10}H_{8};
and the theory generally accepted by those chemists who have been
occupying themselves with these bases and their derivatives is that
pyridine is simply benzol, in which an atom of nitrogen replaces the
triad group, CH, and quinoline, the naphthalene molecule with a similar
change. Indeed, Ladenberg has recently succeeded in obtaining benzol as
an alteration product from pyridine, in certain reactions. Moreover,
from methyl-pyridine, C_{5}H_{4}N(CH_{3}), would be derived an acid know
as pyridine-carboxylic acid, C_{5}H_{4}N(COOH), just as benzoic acid,
C_{6}H_{5}COOH, is derived from methyl-benzol, C_{6}H_{5}CH_{3}, and
from dimethyl-pyridine, C_{5}H_{3}N(CH_{3})_{2}, an acid known as