ADDING THE QUICKSILVER AND MAGISTRAL. 51 



Sometimes, when the reduction is near completion, the quicksilver does not form 

 globules, but is diffused. 



When the limature lias the same color as the amalgam, and gives forth a small 

 amount of silver; when the offal forms a narrow and opaque stripe; finally, when 

 the globule is clear and shining, with little grains on its surface, and, strongly 

 compressed with the finger, gives out an amalgam that makes in the gourd a white 

 mark, — then it may be said that the reduction is going on the right way. If the 

 offal be ash-colored, and the limature rather opaque and soft, thus showing its being 

 overloaded with quicksilver; if, besides, the color of the globule be dark-gray, and 

 the amalgam it contains, on being separated by pressure, leaves on the goiud a 

 track very prominently white-colored, producing something like whitish smoke, — 

 then it is said that the cake is hot. The degree of heating is estimated by the 

 evidence of the aforesaid features. When the lis and limature are very scarce, and 

 the latter too juicy (the globule being elongated and depressed, yellowish or 

 lilackish colored), and the amalgam rendered by it leaves no track on scraping the 

 goiud, then it is said that the cake is cold. 



In the trial made after the stirring following the incorporation, if the ore be 

 not very rich, a narrow offal stripe and a small quantity of limature are all that 

 appear at the top. hence, at the beginning of the reduction, if the ore be poor 

 and rebellious, there is rather no other guidance than the quicksilver globules. 



When the cake becomes hot during the first reduction days, the evil may be 

 prevented by adding either a certain quantity of fresh mud from the reservoir, 

 or some precipitate of copper; but, should the heating be noticed at the end of the 

 operation, precipitate of copjier, ashes, and salt should be put in. 



The action of cold is overborne by throwing into the cake a small cjuanlity 

 of magistral^ or sulphate of copper, in order to increase its strength. 



When the reduction process goes on rightly, it may be noticed, that, on the 

 twentieth day, the limature and metallic sediment the silver contains begin to 

 decrease, while the globule abounds with amalgam; but those effects never appear 

 before the thirtieth day when the ore is rebellious. 



On the cake being ready, a rapid increase of quicksilver lis is noticed, which, 

 rubbed with the finger, becomes c|uicksilver globules, the limature disappearing at 

 the same time. But, although those features are very prominent, they may in 

 many an instance be deceitful. Such is especially the case when quicksilver is 

 in excess, and salt scarce, either for not having put at first the necessary quantity 

 of it, or for it having been consumed or carried out by the rain-water. In order 

 to avoid perplexity, the amalgam is assayed, thus ascertaining the amount of silver 

 extracted ; and this indication, in conjunction with the other characteristics previ- 

 ously found, gives the certainty that no larger amount of silver is to be extracted. 



The above assays serve not only to show the yielding of the cake, but also the 

 daily progress of the reduction process. It is a curious fact to be observed, that 

 the results of the assays go on in a jxirallel line, so to say, with the indications of 

 the amalgam, as hitherto e.xplained ; so that those two means complete each other. 



Washing. — The reduction being finished at the yard, the cake is washed in order 

 to separate the mass of crude metal from the muddy and terreous part. The 

 washing-place is formed by three or four large wooden or stone and mortar vats 

 communicating with each other through large square holes called bilitroues. The 

 first and last of said vats have also outside openings, — the first one to receive the 



