  We have expanded upon earlier work that investigates the relative importance
of coronal loops with isothermal $versus$ multithermal cross-field temperature
distributions. These results are important for determining if loops have
substructure in the form of unresolved magnetic strands. We have increased the
number of loops targeted for temperature analysis from 19 to 207 with the
addition of 188 new loops from multiple regions. We selected all loop segments
visible in the 171-\AA\ images of the Atmospheric Imaging Assembly (AIA) that
had a clean background. 86 of the new loops were rejected because they could
not be reliably separated from the background in other AIA filters. 61 loops
required multithermal models to reproduce the observations. 28 loops were
effectively isothermal, that is, the plasma emission to which AIA is sensitive
could not be distinguished from isothermal emission, within uncertainties. 10
loops were isothermal. Also part of our inventory were one small flaring loop,
one very cool loop whose temperature distribution could not be constrained by
the AIA data, and one loop with inconclusive results. Our survey can confirm an
unexpected result from the pilot study: we found no isothermal loop segments
where we could properly use the 171-to-193 ratio method, which would be similar
to the analysis done for many loops observed with TRACE and EIT. We recommend
caution to observers who assume the loop plasma is isothermal, and hope that
these results will influence the direction of coronal heating models and the
efforts modelers spend on various heating scenarios.
