resizing canvases

book.tex

@@ -3900,8 +3900,8 @@ and second element is a 2-tuple.
 
 \begin{figure}[tbp]
 \centering
-\includegraphics[width=0.95\textwidth]{copy-collect-1} \\
-\includegraphics[width=0.95\textwidth]{copy-collect-2}
+\includegraphics[width=\textwidth]{copy-collect-1} \\[5ex]
+\includegraphics[width=\textwidth]{copy-collect-2}
 \caption{A copying collector in action.}
 \label{fig:copying-collector}
 \end{figure}
@@ -3999,9 +3999,8 @@ be popped back into the local variables because the locations of the
 pointed-to objects will have changed.
 
 \begin{figure}[tbp]
-\centering \includegraphics[width=0.7\textwidth]{shadow-stack}
-\caption{Changing from just a normal stack to use a root stack
-   for pointers to facilitate garbage collection.}
+\centering \includegraphics[width=0.7\textwidth]{root-stack}
+\caption{Maintaining a root stack for pointers to facilitate garbage collection.}
 \label{fig:shadow-stack}
 \end{figure}