Feijkuary 17, 1 9 10] 



NA TURE 



457 



effect of weathering during the hot months on both the 

 yield and quality ot wheat is being ascertained. 



A. Howard. 



G. L. C. HOU'ARD. 



Pusa, November iS, 1909. 



A Note on the Gilded Metal-work of Chiriqui, 

 Central America. 



Among the minor ethnological problems which America 

 offers in such variety, not the least interesting is that of 

 the origin, significance, and method of production of the 

 specimens of gold-work found so abundantly in certain 

 parts of Central America and in the north-western regions 

 of the southern continent. 



The earliest European voyagers who reached the shores 

 of the New World directed attention in their narratives 

 to the gold ornaments and little images of " frogs, birds 

 and men " found in the hands of the natives, and, as 

 Humboldt urged long ago, arguing erroneously from the 

 accumulated riches of generations of savages, they 

 attributed great mineral Wealth to the newly discovered 

 lands, giving them such sounding names as Costa Rica 

 and Castillo del Oro. 



Articles of gold ^lloy are widely distributed throughout 

 South America, and vary as greatly in artistic and 

 technical e.xecution as in the purity or baseness of the metal 

 from which they have been fashioned. This metal-work 

 has long been known to students, as well as to treasure- 

 hunters, and is of so e.xtraordinary a character that it at 

 once attracts attention. Running riot, heedless of the 

 proprieties, its motives include every variety of zoomorphic 

 design — human, bestial, bird, fish, or reptile; all types of 

 life are represented, together with monstrosities and 

 ambiguous shapes bordering frankly on the diabolical. 



A certain amount of South American metal-work finds 

 its way every year to England through dealers who pur- 

 chase it from natives and speculators who make it their 

 business to explore the ancient burial places. Practically 

 the whole of this is melted down on account of its intrinsic 

 value, but it is comparatively seldom that objects of artistic 

 or archajological interest are lost to science in this manner, 

 by far the greater portion of the work being of the crudest 

 description. 



The present letter deals more particularly with the gilded 

 metal-work of Chiriqui, on the southern boundary of Costa 

 Rica, which presents features of peculiar interest. It has 

 been studied carefully by Holmes, whose work on the 

 subject, embodying references to the earlier literature- deal- 

 ing with it, is to be found in the report of the Bureau of 

 Ethnology for the years 1884-5. 



The immediate interest of the subject turns upon the 

 occurrence of objects fashioned from copper-gold alloys of 

 very variable composition, the latter metal being present 

 in some instances in a proportion insufficient sensibly to 

 alter the colour of the copper, whilst, nevertheless, the 

 surface of the objects presents a burnished coating of fine 

 and splendent gold. In many examples the film of precious 

 metal is so slight that it has all the appearance of electro- 

 plated work, and many conjectures have been hazarded to 

 explain the method by means of which the native artist 

 produced the effect. ' 



Holmes, in the treatise already cited, quotes, on the 

 authority of Bollaert, a reference to the works of Acosta 

 to the effect that the Indians of New Grenada gilded copper 

 by rubbing it with the juices of certain herbs and after- 

 wards subjected it to the action of fire, when it took the 

 gold colour, but states that he had not been able to find 

 the passage in question. The present writer has also 

 searched the pages of Acosta in vain, but it is probable 

 that Bollaert quoted from memory the following passage 

 in the " History of the Indies " of Gonzalo Fernandez de 

 Oviedo (Edit. Amador de los Rios, vol. iv., p. i8q), 

 where that writer says, freely to translate the para- 

 graph : — " I would wish to say how the Indians [of the 

 .Antilles, and especially those of Hayti] know well how 

 to gild the little things they make of copper, very yellow 

 , like gold. They have in this such skill and excellency, and 

 give such a deep lustre to that which they gild that it 

 seems to be ^ood gold of 23 carats or more by its colour 

 ^when it leaves their hands. This they do with certain 

 ' NO. 2103, VOL. 82] 



herbs, and is such a great secret that whoever of the 

 goldsmiths of Europe or of any other part shall find it 

 out, he will be a very rich man, and that in a very short 

 time if he uses this manner of gilding." The old historian 

 of the Indies made efforts to learn from the Indians this 

 secret process, but they excused themselves on the plea 

 that the herbs made use of were unknown to them, and 

 that the small quantity they possessed of them came from 

 very distant countries. 



" It is not impossible," says Holmes, " that an acid may 

 have been applied which tended to destroy the copper of 

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

 could afterwards be burnished down. ... It is possible 

 that the film of gold may in some cases be the result of 

 simple decay on the part of the copper in the alloy . . . 

 but the surface in such a case would not be burnished, 

 whereas the surfaces of the specimens are all neatly 

 polished." 



The operation above mentioned, whereby the apparent 

 quality of articles of gold alloy is improved by the artificial 

 enrichment of the superficial layer, is one frequently prac- 

 tised among goldsmiths, who term it "colouring." A 

 hot process, involving the use of fused salts, is generally 

 made use of (viie T. K. Rose, " Metallurgy of Gold," 

 edit. 1906, p. 19; W. T. Brantt, "Metallic Alloys," 

 London, 1896; and Gee, " Goldsmith's Handbook," 1881). 



Considering it probable that a germ of truth lay in the 

 information given by the Indians to Oviedo, the writer 

 made several experiments of a simple character to 

 endeavour to clear up this point. It was found that by 

 acting upon a base alloy with dilute nitric acid, a black 

 lustrous film of gold could be readily obtained by removing 

 in solution a portion of the copper. By heating the object 

 thus treated out of contact with air, the black film of 

 gold is annealed, changing to the yellow modification, and 

 is left in a condition to be readily burnished with any 

 suitable implement, for example, a water-worn pebble of 

 quartz. 



The mineral acids being, presumably, unknown to the 

 craftsmen of pre-Colombian America, advantage was taken 

 of the solubility of copper in organic acids in the presence 

 of air, and after a few successful preliminary experiments 

 with the pure chemical products, various acid plant juices, 

 the " herbs " of Oviedo 's Indians, were tried, and fully 

 answered expectation. There can be little doubt that the 

 Indians had no need to ransack " distant countries " for 

 the wherewithal to gild their ornaments ; but every craft 

 has its mysteries. 



It was found that among the various organic sub- 

 stances tried in the course of the experiments few effected 

 the required reaction so readily as urine, which, with free 

 access of air, rapidly covers the surface of the alloy with 

 a coating of hydrated copper salt readily soluble in acid 

 plant juice. When performed with the aid of these natural 

 reagents, the operation is a very tedious one, the gold 

 filni, in the case of base alloys, taking months to acquire 

 sufficient substance to admit of being burnished ; but time 

 signifies little to the savage. 



In conclusion, although not desirous of affirming that the 

 procedure described was that invariably followed by the 

 Indians in the production of gilded work, the writer is 

 decidediv of the opinion that their operations broadly 

 followed the lines indicated in the present letter. 



Oswald H. Evans. 



" Arauco," South Harrow, February i. 



Suggested Common Dav of Meeting for London 

 Societies. 



Will you permit me to make a suggestion regarding 

 the days of meeting of learned societies in London ? At 

 present these days seem to be selected in a very arbitrary 

 manner, with the result that the provincial members of 

 the societies are often called to London on several days 

 during the same week. For instance, last autumn I ought 

 to have attended no fewer than four such meetings during 

 the same week, namely, on Monday, Tuesday, Thursday, 

 and Friday. It is, of course, impossible for the majority 

 of provincial members of London societies to give up so 

 many days — we are generally compelled in such circum- 

 stances to abandon all the meetings. By some curious law 



