JF Ptak Science Books Quick Post
[Source: Harpers Weekly, February 9, 1879]
B.K. Bliss and sons came up with this idea to distinguish their ad, the one among many, on a full 16″x11.5″ page of Harper’s Weekly. The original is 1.75×2.25″, so it is rather small, but it swims sort of free and clear on the page of 30+ advertisements because of its high contrast.