  We exhibit, by compiling all data sets we can acquire, that the Fourier
frequency dependent hard X-ray lags, first observed in the analysis of
aperiodic variability of the light curves of the black hole candidate Cygnus
X-1, appear to be a property shared by several other accreting black hole
candidate sources and also by the different spectral states of this source. We
then present both analytic and numerical models of these time lags resulting by
the process of Comptonization in a variety of hot electron configurations. We
argue that under the assumption that the observed spectra are due to
Comptonization, the dependence of the lags on the Fourier period provides a
means for mapping the spatial density profile of the hot electron plasma, while
the period at which the lags eventually level--off provides an estimate of the
size of the scattering cloud. We further examine the influence of the location
and spatial extent of the soft photon source on the form of the resulting lags
for a variety of configurations; we conclude that the study of the X-ray hard
lags can provide clues about these parameters of the Comptonization process
too. Fits of the existing data with our models indicate that the size of the
Comptonizing clouds are quite large in extent ($\sim$ 1 light second) with
inferred radial density profiles which are in many instances inconsistent with
those of the standard dynamical models, while the extent of the source of soft
photons appears to be much smaller than those of the hot electrons by roughly
two orders of magnitude and its location consistent with the center of the hot
electron corona.
