Or the crystallization may be irregular; or the substance may not
be quite pure; and if we consider how minute a quantity of matter will
alter greatly the conducting power of water, it will seem not unlikely that
a little extraneous matter diffused through the whole or part of a cube,
may produce effects sufficient to account for all the irregularities of
action that have been observed.

1699. An important inquiry regarding the electrical polarity of the
particles of an insulating dielectric, is, whether it be the molecules of
the particular substance acted on, or the component or ultimate particles,
which thus act the part of insulated conducting polarizing portions
(1669.).

1700. The conclusion I have arrived at is, that it is the molecules of the
substance which polarize as wholes (1347.); and that however complicated
the composition of a body may be, all those particles or atoms which are
held together by chemical affinity to form one molecule of the resulting
body act as one conducting mass or particle when inductive phenomena and
polarization are produced in the substance of which it is a part.

1701. This conclusion is founded on several considerations. Thus if we
observe the insulating and conducting power of elements when they are used
as dielectrics, we find some, as sulphur, phosphorus, chlorine, iodine,
&c., whose particles insulate, and therefore polarize in a high degree;
whereas others, as the metals, give scarcely any indication of possessing a
sensible proportion of this power (1328.), their particles freely
conducting one to another. Yet when these enter into combination they form
substances having no direct relation apparently, in this respect, to their
elements; for water, sulphuric acid, and such compounds formed of
insulating elements, conduct by comparison freely; whilst oxide of lead,
flint glass, borate of lead, and other metallic compounds containing very
high proportions of conducting matter, insulate excellently well. Taking
oxide of lead therefore as the illustration, I conceive that it is not the
particles of oxygen and lead which polarize separately under the act of
induction, but the molecules of oxide of lead which exhibit this effect,
all the elements of one particle of the resulting body, being held together
as parts of one conducting individual by the bonds of chemical affinity;
which is but another term for electrical force (918.).

1702. In bodies which are electrolytes we have s