At first glance, there appears to be little of interest in this image. Two barely outlined chimneys rise ghostlike from what the title identifies as a rooftop. Looking again at the date of this image makes its significance clearer. This photogenic drawing negative was made around four years before the invention of photography was announced to the public, when William Henry Fox Talbot was still experimenting with light sensitive chemistry and optical devices.
In this instance he used a camera obscura to project the light that was reflected off the building through a lens fitted onto the camera obscura. A piece of light-sensitive paper was taped at the back of the camera obscura. The reflection of the building was registered on the paper, which produced this sketchy negative image of the building. Talbot conducted these light-sensitivity experiments from mid-1834 until the summer of 1835. In early January 1839, he learned about Jacques Louis Mandé Daguerre's impending announcement of his daguerreotype process in France; two weeks after Daguerre's announcement, Talbot published his invention of the photogenic drawing.