This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
RowlandGrating. en January en picture of Henry Augustus Rowland's grating ruling engine own original text created this work entirely by myself Chhe talk Chhe Original upload log page en RowlandGrating Chhe bytes no picture of Henry Augustus Rowland's grating ruling engine created this work entirely by myself June Henry