COMPOSITIOX OF ORES. 549 



alogy the relations of bromine to chlorine vary from 1:0.33 to 1 :5.67, 

 but no iodine is given. In I and II, given above, the relations are 1 :0.16 

 and 1:0.11, and all three contain a small amount of iodine. 



According to Moesta,^ in the mines of Chanarcillo, Chili, there is a 

 regular gradation in these compounds according to depth, the pure chlorides 

 being found in the upper levels down to a depth of 20 meters; below these 

 come mixtures, containing proportions of bromide increasing with the depth; • 

 still lower iodide of silver is added to the mixture, and pure iodide of silver 

 occurs at sixty to seventy meters in depth, directly over the deposits of 

 galena and pyrite, in which the first sulphides of silver are found. It has 

 not been possible to detect any regularity whatever in the distribution of 

 these compounds in the Leadville deposits. The colorless and green chlo- 

 rides are the prevailing varieties, but minute yellow crystals of iodide of 

 silver have been observed in the deposits of the Chrysolite mine. 



In Chanarcillo among secondary deposits about half the silver occurs 

 in the native state, and of the other half the far greater proportion occurs as 

 chloride or chloro-bromide, iodides being rare and the proportion of iodine 

 in the mixture being very small. Thus, according to Moesta, from whose 

 work all these statements are taken, the relative proportions of chlorine, bro- 

 mine, and iodine are essentially the same in which they exist in sea-watei\ It 

 may be added that the same relations exist in surface waters, and in rocks 

 whenever these substances have been detected in them. Moesta's theory 

 with regard to the chlorides, &c., of Chanarcillo, that they were formed by 

 the action of sea-water (since there is evidence that the region has been 

 covered by the ocean within comparatively recent times), would not apply 

 to the Leadville deposits, for the reason that they have not been submerged 

 since the upheaval and erosion that brought them within the reach of sur- 

 face waters. 



Basic ferric sulphates. — In the foUowiug table are given the analyses of 

 three specimens, contributed by Mr. L. D. Eicketts, from material observed 

 by him to frequently constitute a persistent bed under the rich ore bodies, 

 especially on Carbonate Hill. This material is of ocherous-yellow color, 



' Chlor-, Bmm- iiml Jodverbindungen des Silbers in der Natur. Dr. Fr. A. Moesta. Marburg, 1870. 



