ink spot

Otherwise it was so very tiny that it lay upon its red rug like an ink spot on a piece of blotting-paper.

It grew larger and larger, a half hour later spreading overhead like a dark ink-spot on a beautiful robe of blue.

His downward drawn mouth was ajar, and he was gazing blankly at a familiar ink spot on his desk.

You know Nellie has found the ink-spot on the other mat by this time, and there's no way to give her this one back.

You see my—your—the mat with the ink-spot on it is nearly finished now, so I have done about as much work on one as on the other.