Steps to reproduce the issue

Upload one or more images to joomla media directory, size approximately 100px x 100px.
Create an article category called "Test". Articles > Categories > New.
Create 2 or more articles, set their category to "Test".
For each article Add a minimal amount of text to each article, only one or two lines of text.
For each article, under the Images and links tab, add an intro image approximately 100px x 100px.
Add a menu item to the Main Menu. Menu Item Type = Articles > Category Blog. Under choose a category, select your "Test" category.
Under the Blog Layout tab, set # of Leading Articles to 100.
Go to your website and use the new menu link to view your category blog page. The second article title does not clear the 1st article.

Expected result

Each Article should clear the prior article.

Actual result

The second article heading is directly next to article #1's image.

System information (as much as possible)

Joomla 3.4.4. Tested on Chrome, IE 11

Additional comments

It looks like the class for each article, dynamically named "leading-0", "leading-1" etc needs css style: CLEAR:BOTH. Alternatively, look at the layout of menu item type "Featured Articles", this is similar to the blog layout, but does not exhibit the same issue.