As I understand it, there are basically two types of mud-and-stick
chimneys associated with American log cabins and houses.  The first, and
most probable for your part of Virginia, is the 'pen' type.  With few
exceptions the chimney was located in the exterior center of one of the
gable ends.  A large hole was cut in the log wall from the floor up the
height and width of the fireplace.  Both chimney/hearth types were
constructed as three walls around this opening with the upper portion of
the chimney stack (enclosed on four sides naturally) built as far away
from the log wall as possible.  The 'pen' chimney was built much in the
manner of the house itself.  The base of the chimney was formed of
interlocking, alternating tiers of short logs notched into the wall logs
of the house surrounding the fireplace opening.  These logs were chinked
in the usual manner and covered with an extra thick layer of mud or clay
daubing.  Stones (and sometimes brick and mortar) were set flat, for
hearth, and built up on the inside of the log pen and well daubed to
make the firebox.  Above this structure the flue was constructed of
smaller logs and sticks stacked 'cob-house style' (in tiers like log
construction but not necessarily notched at the corners) and well
covered with clay.  It is believed that no original survivals of this
type of chimney exist; more likely, one has yet to be found.
 
The second type of mud-and-stick chimney is the 'cat' or 'catted'
chimney, which was essentially a wattle-and-daub technique.  The 'cat'
chimney was built by constructing a pole framework defining the exterior
form; usually four poles, two against the end wall and two on the outer
end of the chimney.  Horizontal slats were inserted between the poles
approximately 8" to 10" apart.  Later examples were sometimes built with
nails, but nailing wasn't necessary.  The slats could also be fastened
by  inserting sharpened, pointed ends into holes or grooves, and with
pegging and lashing there may be no hardware at all.  This framework was
then filled with mud 'cats' and daubed over.  The 'cats' were formed by
mixing a binder (hay, straw, moss, animal hair, etc.) in a clay pit and
molding rough bricks, or "matlike rolls" about 4" thick and a foot
long.  According to Terry Jordan, this type of chimney most commonly
occurred in the "coastal plain of the Lower South and the adjacent
Ouachita Mountains of Arkansas." (Jordan:98)  Henry Glassie documented
one in Arkansas as newly constructed in 1964. ("Pattern":114)
 
Both chimney types were 'cured' with an initial, carefully controlled
fire to bake and harden the clay daubing.  It should also be mentioned
that some log houses (technically 'cabins') had *no* chimneys and relied
instead on a simple smoke hole in the roof above the earthen hearth.
 
Although I have done some digging, for classes and for hire, I am not an
archaeologist, but I can venture some speculations about the possible
archaeological evidence for such structures.  Glassie illustrated with
drawings two catted chimneys:  one was on a low stone
foundation--probably the hearth extended, and the other appears to have
been earthfast.  In other words, you may or may not find small
postholes.  The 'pen' type of chimney (more likely what you will be
finding) was built directly on the ground and would probably leave
little in the way of features.  On the other hand, these chimney types
were notorious for catching fire.  There are numerous accounts of
slaves, as well as white inhabitants of log cabins, keeping a large pole
or two leaning against the house to be used to push the chimney over
when it caught fire.  (These poles can be seen in many of the
contemporary illustrations of slave cabins.)  Depending on the quality
of clay used, and if you're extremely lucky, you may be able to find
bits of charred, hardened clay, perhaps complete with stick
impressions.  Because of the practice of pushing over burning chimneys
you may also want to extend your search to say, 10'(?), beyond the end
of the cabin.  There may also be some stone rubble from the remains of
the firebox, and I would be very suspicious of any chunks of clay that
appear out of character (I know this may be difficult task in some parts
of Virginia <g>).
 
I would also be interested to know if you find any small postholes
outside the entrance of the cabin(s).  One feature that I've heard
little mention of, but have seen in Civil War era engravings, is the
brush-arbor porch.  This consisted of two large forked sticks driven
into the ground about 8 to 10 feet apart and about 7 feet high.  A pole
was laid in the fork, parallel to the cabin, and this supported the
front of an arbor which was tied to either the roof or the plate of the
cabin.  A lattice of smaller poles on top held a pile of brush, probably
evergreens, which made one of the simplest and oldest style of porch
ever seen.
 
For chimneys on log houses, see:
 
Henry Glassie, _Pattern in the Material Folk Culture of the Eastern
United States_, University of Pennsylvania Monographs in Folklore and
Folklife, No. 1 (Philadelphia, PA:  University of Pennsylvania Press,
1968) 113-114.
 
Terry G. Jordan, _Texas Log Buildings:  A Folk Architecture_ (Austin,
TX:  University of Texas Press, 1978) 95-103.
 
My apologies for the length; I hope this is of some use.
 
Marty Perdue
(Doctoral candidate in architectural history, Univ. Virginia)
[log in to unmask]