transition along the melting curve for as far as we can map it out. There is no sign of it ending at an “upper critical point" as has been often suggested by experimental works.[@Khaykovich; @Nishizaki] Choosing the minimum in the $P(\Delta S)$ histogram as the dividing point, we assign each configuration as a vortex lattice or vortex liquid according to the value of $\Delta S$ for that configuration. Having divided configurations into distinct lattice and liquid states, we can then construct the histograms of energy, $P(E)$, and of the disorder conjugate variable, $P(Q)$, for each state respectively. In Figs. \[f4\]b,c we show such histograms for disorder strength $p=0.12$, corresponding to the data of Figs. \[f3\] and \[f4\]a. We see for both $E$ and $Q$ well separated histograms for lattice and for liquid states. Using these histograms we then compute the average $E$ and $Q$ separately for the vortex lattice and vortex liquid, and then compute the discontinuities in these quantities at melting, $$\begin{aligned}
\Delta E &\equiv& \langle E\rangle_{\rm liquid} - \langle E\rangle_{\rm lattice}\\ \nonumber
\Delta Q &\equiv& \langle Q\rangle_{\rm lattice} - \langle Q\rangle_{\rm liquid}
\label{DEQ}\end{aligned}$$

=8.6truecm

In Fig. \[f5\]a we plot (open symbols) the resulting $[\Delta E]$ and $[\Delta S]$, 