1880, ] Geology and Palecniology. 685 
diffused and eminently suited for building purposes, both on 
account of their hardness and stratification. 
B. Metals—tr. Iron ores; a, spar iron ore, or spherosiderite, 
pure and clayey; 4, brown iron ore; c, yellow iron ore, as bean 
ore and limonite ; d, hematite and ironglance, or silicate of iron. 
2. Copper ores; a, malachite; copperglance; c, azurite. 
3. Zinc ores; a, zincspath; 4, zincblende. 
4. Lead ore; as leadglance. : 
60 feet thick, are almost always overlaid with sandstone or lime- 
stone ; all iron ores are contained in these clay deposits, and laid 
in compact masses, 2 inches to 2 feet thick, in more or less regu- 
lar strata or in pockets 
Brown iron ore is séldom deposited as such in clay, but appears 
mostly from spherosiderite, exposed to the air and weather- 
Through the influence of succeeding geological periods, the 
sandstone and limestone covering the clay strata were in some 
places destroyed; the soft clay laid bare was in the course of time 
by rain washed away, and thus there were produced the valleys, 
bluffs, hollows and ravines. The heavy masses of iron ores 
remained behind, and have by degrees so accumulated that there 
are stretches a mile wide on which hundreds of tons of iron ore 
can be gathered on the surface of one acre, without the aid of 
shovel or pick. When the spherosiderites are disintegrated and 
washed out they often acquire the appearance of slag, and have 
therefore formerly been taken for volcanic scoria. 
_The iron ore of the permian period of north-western Texas is 
diffused over a surface which extends over more than one hun- 
dred miles in length and over fifty miles in width. The outwashed 
and cleansed mass on the surface is so large that it would suffice to- 
Supply the whole United States with iron for ten years. 
spherosiderite, containing zinc. ‘Lead is found sparingly injected 
in spherosiderite and very hard clay masses. I have nowhere 
