What does "copygraph" mean?

Copygraph: A contrivance for producing manifold copies of a writing or drawing. Note: The writing or drawing is made with aniline ink on paper, and a reverse copy transferred by pressure to a slab of gelatin softened with glycerin. A large number of transcripts can be taken while the ink is fresh. Various names have been given to the process [the gelatin copying process], some of them acceptable and others absurd; hectograph, polygraph, copygraph, lithogram, etc. Knight.