  The observations from 1998 April 20 taken with the Coronal Diagnostics
Spectrometer CDS on SOHO of a coronal loop on the limb have shown that the
plasma was multi-thermal along each line of sight investigated, both before and
after background subtraction. The latter result relied on Emission Measure Loci
plots, but in this Letter, we used a forward folding technique to produce
Differential Emission Measure curves. We also calculate DEM-weighted
temperatures for the chosen pixels and find a gradient in temperature along the
loop as a function of height that is not compatible with the flat profiles
reported by numerous authors for loops observed with EIT on SOHO and TRACE. We
also find discrepancies in excess of the mathematical expectation between some
of the observed and predicted CDS line intensities. We demonstrate that these
differences result from well-known limitations in our knowledge of the atomic
data and are to be expected. We further show that the precision of the DEM is
limited by the intrinsic width of the ion emissivity functions that are used to
calculate the DEM. Hence we conclude that peaks and valleys in the DEM, while
in principle not impossible, cannot be confirmed from the data.
