Capping
The capping or
also topping of a (Roman) kiln
comprises the material used as temporary
covering for the open end of the superstructure. Its purpose was to
prevent the loss of heat but also in the case of reducing firing, to
prevent oxygen intrusion.
Carolingian
Denotes a time
between the 8th and 10th century AD were a dynasty of Frankish rulers
(amongst them Charles the Great) and their successor ruled parts of
Europe (mainly territories in the present day France, Germany and
Austria).
Characteristic remanent magnetisation (ChRM)
Remanent
magnetisation obtained after removal of less stable remanent
magnetisation components. It represents in general the record of the
Earth magnetic field
at the moment of cooling of a baked clay (see also remanence).
Chemical remanent magnetisation (CRM)
Remanent magnetisation acquired during the
crystallisation of magnetic minerals
in a magnetic field.
Classical Period
Cultural period
in Greece between 500 and 336 BC subsequent to the Archaic period and followed by the
Hellenistic period.
Developments culminated in Athens in politics
(Pericles), culture (Sophocles,
Euripides) and philosophy (Socrates, Plato).
Coercivity
Magnetic field
that must be applied to a material to change its magnetisation in the
opposite direction. The coercivity depends inter alia on grain size and
grain shape. When remanent
magnetisation is concerned one speaks about coercivity of remanence.
Coercivity spectrum
A variety of
grain sizes and shapes exist in a sample or specimen. Hence, the
coercivity is rather a distribution of values than a
single value. This
is called coercivity spectrum.
Combustion chamber
Part of a kiln,
where the fire burns and from which hot gases percolated upwards
through the raised oven
floor to the overlying oven.
In single
chambered sunken kilns it is also called oven-pit.
Concentration parameter k
Approximation
for the concentration parameter κ of the Fisherian statistics.
Indicates the statistical distribution of point on the surface of a
sphere and is a scatter estimate of for ChRM directions. κ ~ k = (N-1)/N-R);
N – number of directions, R – modulus of the vector sum of
all unit vectors. A mean ChRM
direction of a site should have values of
k > 80 to be considered as
reliable result.
Confidence factor α95
Semi-angle of
the cone of confidence around the mean direction in which the true
direction occurs with a confidence level of 95%. It is calculated from
the
following formula α(1-P) = cos-1(1-
(N-R)/R[(1/P)1/N-1-1])). N – number of directions, R – modulus of the vector sum of
all unit vectors, P – is the
probability and is usually 0.05. This means that one is 95% to find the
unknown true mean direction within the α95 of the calculated
mean. For a mean direction
of an archaeological site α95
should not be more than 2°. In order to assess the accuracy of a
mean direction, the concentration
parameter k should also
be considered,
because smaller α95 can be obtained by
increasing the number of samples.
Context dating
Relative
dating of an archaeological structure or object based on other
archaeological findings around with known age.
Cryogenic magnetometer
Instrument to
measure the remanent
magnetisation of rock and baked clay samples based
on certain superconducting properties. The sample to be measured is
inserted in a superconducting coil in which it induces a persistent
electrical current. This current is send to another coil via a magnetic
flux transformer. The amplified current is then detected by a sensor
called SQUID-sensor,
in reality a weak magnetic field detector. The
superconducting coil consists in fact of three pairs of orthogonal
coils that can measure simultaneously the three
orthogonal
vector components of the magnetisation. Its main advantages compared to
the spinner magnetometer are its high sensitivity, short response time
and a signal independent of the velocity with which the sample is
inserted in the detection coil.
Curie, Pierre
French physicist
(Paris 1859 – Paris 1906). He studied the magnetism of materials as a
function of temperature and deduced from it the “principle of
symmetry”: the symmetry of elements of causes of physical phenomena
must be found back in the effects. He deduced from it also a law, χ = C/T,
expressing the decrease of the magnetic susceptibility of paramagnetics
with increasing temperature, known as the Curie-Weiss law. With his
wife Marie Curie he studied the phenomenon of radioactivity and
discovered with his brother Jacques, piezoelectricity. He obtained the
Nobel Price in 1903.
Curie-temperature TC
Temperature
below which, magnetic
moments of ferromagnetic
materials are parallel.
Beyond this critical temperature they become paramagnetic.