Mac Mail Display Problem

My incoming emails appear on the left of my screen and the messages used to appear in full view to the right. All of a sudden now I get the listing of new emails on the right and the only thing I can get to display on the right is the header. I have looked every where for a solution so that my emails display when selected, but I simply can not find it. I would think this would be an easy thing to find under "view" but I have come up empty.
If this makes sense to anyone and they can shed some light on this for me, I would be very grateful. Thanks!

OK, took a bit of experimenting, but this is how I got it to show the email on the right. Hide the list of mailboxes, then the preview pane will slide a bit in from the right, where you can then adjust the width of the center column so that the preview is larger. Then Unhide the mailboxes again. The Hide/Unhide is on the tool bar just above the email headers for mailbox, sort by, etc. It may also be possible to drag the right edge of the text window to the left, but I couldn't get the cursor to drag that and NOT the right edge of the whole window.