Didot

1. Reference in Johnson

In his 1873 paper {" On Certain Improvements in the Manufacture of Printing Types "}, J.R. Johnson notes:

"In France, Henri Didot had, thirty years previously, had [sic] invented his Polymatype, by which 200 letters were made at one stroke of the machine, and this could be repeated at least twice a minute. By this machine the most perfect types were produced, for each letter was cast in a groove made specially for it, of the exact dimensions required." (330; Google PDF p. 341).

It is not clear from the context whether "thirty years previously" refers to 30 years before the date of this paper (1872-30 = ca. 1842) or 30 years before the Great Exhibition (1851-30 = ca. 1821).

Johnson also notes that the foundry of "Messrs. Thoret-Viret ... are using the Polymatype apparatus to this day." (330)

Finally, Johnson notes that:

Mr. Henri Didot, inventor of this ingenious process, and of the tools of precision by which he was able to construct it, sold the patent-right of the invention to a M. Pouchée [sic], who, in partnership with Mr. Jennings, commenced a foundry, and cast a large quantity of type by machine, but ultimately succumbed to the vigorous hostility of the associated founders." (330)

2. Reference in Powell

{ Powell. A Short History of the Art of Printing in England. (1877) , p. 34} cites without further reference Henri Didot as an investigator of typecasting machines.

3. Reference in Ponchée's Patent Abridgment

The GB patent No. 4826 of 1832-08-05 by Louis John Ponchée [sic] was communicated by "Didot, of Paris." See the Notebook on Pouchée for further discussion.