SPEISS, 



721 



Tbe powder of the vesicular s])eiss was uot analyzed, as Las been stated before, 

 but it is probable tliat its conipositiou aud formula are the same as that of the preccd 

 iug, siuce both are saturated speiss aud coutaiu au excess of uou combiued irou. 

 Ilowever, both cannot be considered as mere mixtures of definite arseuio-sulphu- 

 rets of iron and iron, for botli the iron and the arsenio sulphuret are crystalline, aud 

 they are iu all probability crystallographic compounds.^ It has been seen that slags 

 were similarly crystallograiihic compounds. It will be seen that mattes also are crys 

 tallographic com[)ounds. A few remarks will be made with. regard to slag-u)attes, which 

 form the highest expression of this class of substances, so that in almost every stage 

 of the smelting operatious crystallogra[)hic comi)Ouuds are the regular products of the 

 blast furnaces. 



The speisses analyzed are remarkable ou account of — 



1. The presence of antimony in such very small quantities, whilst it exists iu the 

 smelting charges, and is formed in no iucousiderable quantity in the bullion, the 

 fumes, etc. 



1!. The presence of molybdeuum iu each and sensibly iu the same amount, show- 

 ing how widely and evenly distributed this metal is iu the camp. In the writer's 

 opinion it -is the first time molybdeuum has been jioiuted out in speiss. It is so thor- 

 oughly conceutrated iu this product that it was not possible to detect it in either 

 bullion, slag, or fumes. 



3. The total absence of cobalt, which, as has beeu observed, is concentrated iu 

 the skimmings of the lead of the siphon-tap, and thus thoroughly separated from 

 nickel, which, as the preceding analyses show, remains iu the speiss. 



Assays of speiss for gold and silver — Iu order to Complete the Study of the Leadville 



speiss, the following assays were made of speiss belonging to the three different tyi)es 



iu the Survey laboratory : 



Table XIII. — Assays of sptus. 



'Exactly whiit Mr. G 11 yard means by the term crijstallograpMc compounds 

 MON XII iG 



I am uot able to state. 



