P-V Diagrams look odd 

I noticed the curved lines on the P-V diagram are not labeled and appear to not lie as I would expect. If the curved lines are constant temperature they should appear to run asymptotic to the P and V axis'. I'm not sure how the lines of constant entropy should lie but should probably appear nearly asymptotic to those axis' also. They are only sketches but the lines of constant this or that might be labeled as such. I need to pick up the skill to create such diagrams and other sketches.