This coal hole cover and vault light has an enticing date on it, but it is not the oldest cover in the city. The date of course refers only to the patent by the prolific and influential J.B. Cornell, whose name is frequently seen on cast-iron building fronts in SoHo and other areas. But, the J.B. & J.M Cornell Iron Works was not formed until 1870.
Although badly damaged, this cover still retains some of the finely crafted details that are associated with the Cornell foundry. Notice the finely graded lines on the outer seat and the reinforce hexagons around each glass hole that maximize the amount of light that once passed through it.
Cast iron encased glass plugs were developed in the first third of the 19th century for illumination of underground areas. It was also the time when coal as a household fuel was first widely used. Coal delivery to basement bins led to the combined lid/vault lights, at least for the well to do.
This particular cover is on Clark St. in the Brooklyn Heights Historic district in front of an 1840s house. Other examples of Cornell covers are scattered about the older well-to-do neighborhoods. There are also a number of vault lights that do not include the Cornell name, but which seem to have identical design elements.