DuBois.] ^^ [April 5, 



no right to say that the process described by Mr. Swan is not entirely 

 original with him. It is proper, however, to call the attention of the 

 American Philosophical Society to the following facts. 



At a meeting of this Society held February 16, 1877, William E. Du- 

 Bois, then Assayer of the United States Mint in this city, and a member 

 of this Society, made a brief communication {Proceedings, Vol. xcix) on 

 the production of gold films by a process such as Mr. Swan has within a 

 few months past, through the Royal Society, brought before the public. 

 The inventor of the process was Mr. Alexander E. Outerbridge, Jr., then 

 an assistant in the Assay department of the Mint at Philadelphia and 

 subsequently engaged in establishing and carrying on scientific laborato- 

 ries at the Whitney Car Wheel Works and at the large establishment of 

 William Sellers & Company, both in this city. 



Apart from any future possibility of producing gold leaf by electro- 

 chemical instead of mechanical process, Mr. Outerbridge regarded his 

 results as interesting in a purely scientific aspect. The gold films pro- 

 duced at that time by him seem to have been much thinner than those 

 which were recently shown at the Royal Society by Mr. Swan. Speci- 

 mens were exhibited in the Philadelphia Mint as early as 1877, and some 

 were obtained by several colleges and individuals. One now in the pos- 

 session of Dr. George F. Barker, of this city, is accompanied by the 

 written account which Prof. Barker received with it in 1878. This mem- 

 orandum is as follows : 



"Gold film obtained from a copper plate having 20 square inches sur- 

 face : 



" Weight before plating ^^\md ?^s- 



"Weight after plating. ^^{-5-^5 Si's- 



"Weight of gold yfo^ gi'- 



"Calculated thickness, ^-jyl^-Q^Q of an inch ; 59^ times less than a single 

 wave-length of green light." 



This is mounted as a slide for a microscope, and has a double fold. I 

 have also specimens in my own possession. 



In addition to the brief communication made by Mr. W. E. DuBois to 

 this Society in 1877, as aforesaid, the Journal of the Franklin Institute 

 (Vol. ciii, 284) gave an abstract of a lecture delivered by 3Ir. Outerbridge 

 before the Franklin Institute in 1877. At the stated meeting of the Insti- 

 tute held May 16, 1877, Mr. J. B. Knight, then Secretary, referred in his 

 monthly report to Mr. Outerbridge's process in the following terms : 



" Transparent Gold. — In the course of a lecture on gold, delivered 

 before the Franklin Institute, on February 27lh last, Mr. A. E. Outer- 

 bridge, Jr., of the Assay department of the Mint in this citj', gave an 

 account of some experiments he had made witii tiie view of ascertaining 

 how thin a film of gold was necessary to produce a fine gold color. 



" The plan adopted was as follows : From a sheet of copper rolled down 

 to a thickness ofy/j^of an inch he cut a strip 2^ by 4 inches. This 

 strip, containing 20 square inches of surface, after being carefully cleaned 



