SEM Results: Rowland Grating (ca 1887)

The example that was available for study was broken by Rowland near the end of Stanley MacKenzie’s PhD research project at Johns Hopkins University. He later became president of Dalhousie University, where the grating is preserved.

The broken Rowland grating has a protective overcoating, which would not have been part of the original grating. There are several visible cracks and blotches indicating the presence of a clear lacquer of some sort. Despite the fairly thick layer of lacquer, the grooves can be seen in some detail. As with Rutherfurd’s rulings, the space between the grooves is quite wide, but spacing is more regular on this grating. The efficiency of this grating would likely have been lower than if it had had closer ruling. This was a flat grating, rather than one of the concave gratings which remain Rowland’s most significant contribution to the ruling art.

Electron micrograph of part of the Rowland grating (ca 1890) preserved in the Physics Department at Dalhousie University