Scroll direction reversed

On my homepage, the posts are displayed with newest on the left, oldest on the right. However, when I click into a post, the arrows to go to the next post reverse. For example:

>On the homepage, I click the leftmost (newest) link and scroll to the bottom. The arrow to go to the next post is on the left, rather than the right.

>I click on the link second to the left, scroll to the bottom, and the left arrow navigates me to the post that on the homepage is on the right and the right arrow navigates me to the post that on the homepage is on the left.

How can I reverse this navigation, so that the arrows follows the ordering of the homepage?