Be it known that I, EDWARD J. DOBBINS, a citizen of the United States, and a resident of London, England, have invented a certain new, original, and ornamental Design for Prism-Plates; and I do hereby declare the following to be a full, clear, and exact description of my invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawing, which forms a part of this specification, and in which—

Figure 1, is a perspective view thereof; and, Fig. 2 a view in side elevation.

As shown in the drawing, my prism plate has one face composed of a series of parallel

ribs 1 and the opposite face composed of a series of parallel ribs 2 extending transversely of the ribs 1. Each rib 1 presents in cross-section two curves 3 and 4, the latter (4) following the arc of a circle whose radius is shorter than the radius of the arc of a circle followed by the former (3). Each rib 2 presents in cross-section a substantially prismatic shape.

I claim:

The ornamental design for a prism plate, substantially as herein described and shown.

Witnesses:

H. D. JAMESON,

F. L. RAND.