POOLE ON THE GREAT AMERICAN DESERT. 219 



a nucleus of galena, the purity of which has alone effectually resisted 

 the slow combustion which the favorable conditions for the admission 

 of moisture, warmth, and air, have established in the vein where the 

 more easily decomposable iron pyrites are intermixed with the galena, . 

 we are forced to conclude that a considerable length of time must 

 have passed away since these veins were first exposed by the 

 subsidence ot the lake to the action of the agents of the atmosphere, 

 to allow the decomposition to extend to the depth to which by 

 mining, it is often found to have gone. 



In the veins in the limestones of Camp Floyd and Lyon hill, . 

 the outer portions are found to contain chloride and chloro- 

 bromide of silver, which in depth give place to ruby silver, 

 and at still greater depths, to sulphides and antimonial silver ores. 

 The limestones being open have allowed the action of the elements 

 to transform the sulphides and antimonides into oxides and chlorides 

 of silver, even to a depth of one and two hundred feet. 



The Jordan property, the oldest location in Utah, has enormous 

 deposits of carbonate ore, averaging 60 per cent, in lead, 

 cropping to the surface, which in depth, as soon as water is 

 struck, gives place to unconverted galena. As much of this 

 galena is largely mixed with iron pyrites, which the decompo- 

 sition in the upper portion of the vein changed into sesquioxide of 

 iron, a base rather beneficial than otherwise for the reduction of 

 the ore in the blast furnace, the value of the property which the 

 appearances on the surface indicated is greatly reduced. 



The ores from the great Emma mine also supply excellent 

 examples. The specimens on the table show all the stages of 

 change. The nucleus of each nodule being either of galena or of 

 undecomposed sulphoantimonide of lead and silver, is encased by 

 partially oxidized compounds and carbonate of lead and oxide of 

 silver. 



I have here a very interesting mineral, the remains of a rodent 

 encased in lead ore. It was found in the Silver Exchange on Lyon 

 Hill. The country rock there is limestone ; and fissures penetrate 

 it to a considerable distance. The animal, probably a ground 

 squirrel, to which this portion of a lower jaw belonged, must have 

 S 



