MANNER OF DEPOSITION. 97 



ure of the fissures is plainly visible, and the bowlders in these are angular, 

 showing that they have not been much attacked by water. 



Arrangement of the ore in the chambers. During the investigation of the Eureka 



deposits, upon which this report is based, several favorable opportunities 

 were offered for examining freshly-discovered ore bodies of considerable 

 size. In two of these cases the ore was discovered by following seams 

 stained with ferric oxide. The two places mentioned were above the ninth 

 level of the Eureka and below the sixth level of the Richmond. The ore 

 was struck in both instances considerably below the caves which formed 

 the apices of the chambers. The ore in the lower part of the chambers, if 

 not in what could be called a solid state, was at least in a much more com- 

 pact form than it was in their upper portions. It had the appearance of 

 being in place, that is to say, that of being in the position which it originally 

 occupied when deposited from solutions. With the ore composing the 

 upper portion of these ore bodies it was otherwise; this was in a loose state 

 and often distinctly stratified, the strata being composed of different varieties 

 of ore. There was frequently a layer of gray carbonate of lead, followed 

 by a yellow one composed of a mixture of ferric oxide and plumbic sul- 

 phate, with here and there, through the whole, bunches of galena surrounded 

 by its products of decomposition. 



In the Richmond ore body a small cavity in the ore-mass was observed 

 containing stalactitic columns of minerals, which were evidently formed by 

 crystallization fiom solutions. The layers of ore were covered by layers of 

 sand and gravel and bowlders which formed the bottom of the caves. The 

 whole upper portion of this mass showed clearly that it was brought into 

 its present position by water, and the stratification of the ore proved that 

 it was deposited in its present position since oxidation took place. There 

 were layers of the miners' yellow carbonate, composed of every shade of 

 yellow and brown, which, although some of them were not a sixteenth of 

 an inch thick, were as distinctly defined and as clearly visible to the eye 

 as any layers would be in a piece of shale of unquestioned sedimentary 

 origin. The planes of stratification were rarely horizontal, and this was 

 not remarkable, as a large mass of loose ore in a cave of irregular shape 



and with inclined sides would not settle in a uniform manner, and the strata 

 2C54 L 7 



