HOLMES] USE OF GOLD AND COPPER. 39 



leads to the inference that pieces now in my possession exhibiting 

 this phenomenon may have been tampered with by the whites. In 

 this connection attention sliould be called to the fact that history is 

 not silent on the matter of plating. The Indians of New Granada 

 are said to have been not only marvelously skillful in the manipula- 

 tion of metals, but, according to Bollaert, Acosta declares that these 

 peoples had much gilt copper, '"and the copper was gilt by the use 

 of the juice of a plant rubbed ovm- it. tlieu put into the fire, when it 

 took the gold color."' Just wliat this im-aus we cannot readily de- 

 termine, but we safely conclude that, whatever the jjrocess hinted 

 at in these words, a thin surface deposit of pure gold, or the close 

 semblance of it, was actually obtained. It is not impossible that an 

 acid may have been applied which tended to destroy the coi^jjer of 

 the alloy, leaving a deposit of gold upon the surface, which could 

 afterwards be burnislied down. 



It has been suggested to me that possibly the film of gold may in 

 cases be the result of simple decay on the part of the copper of the 

 alloy, the gold remaining as a shell upon the surface of the still un- 

 decayed portion of the composite metal; but the surface in such a 

 case woiild not be burnished, whereas the show surfaces of the speci- 

 imens recovered are in all cases neatly jaolished. 



If we should conclude that the ancient Americans were probably 

 able to secure in some such manner a thin film of gold, it still remains 

 to inquire whether there may not have been some purely mechanical 

 means of plating. In some of the Chiriquian specimens a foundation 

 of very base metal appears to have been j)lated with heavy sheet gold, 

 which as the copj^er decays comes off in flakes. Occasional pieces 

 have a blistered look as a consequence. Were these people able with 

 their rude appliances to beat gold into very thin leaves? and Had they 

 discovered processes by which these could be applied to the surfaces 

 of objects of metal? are questions that should probably be answered 

 in the affirmative. 



The flakes in some cases indicate a very great degree of thinness. 

 Specimens of sheet gold ornament.? found in the tombs are thicker, 

 but are sufficiently thin to indicate that, if actually made by these 

 lie,, pie. almost any de-Tee of tliiiiuess ciuld be allaiAed by tliem. It 

 wnuhl i,n.l.alil>' ihit hedillieult t(.a|ii.l.\- thin sheet gold to the com- 

 jiaratively suiunth suifaces ,.r thes ■nanieiits and to fix it by bur- 

 nishing. 



Mr. Kunz suggests still another metliod by means of whicli plating 

 could ha\ !■ been accomplished. If a figure in was wetv coated with 

 sheet ,t;olil and tln-n incased in a clay matrix, the wax could he melted 

 out, leaving the shi-ll of gold within. The cavity could then be filled 

 with alloy, the clay could be removed, and the gold, which would ad- 

 here to the metal, could then be properly biirnished down. 



' Bollaert: Ethnological and Other Researches in New Granada, &c. 



