THE NONMETALLIC MINERALS. 



335 



iron oxides, pota.sh unci soda, too'cthcr with linu^ and niaynosia in such 

 ])roi)oi-ti()ns that tiicy vitrify roadily, forniin<>- thus an iiiiju'rvious 

 glass over tiiose poi'tions of the ware to whicii they arc applied. 



The following- analyses show (I) the composition of a slip clay us(>d 

 in ])()ttery works in Akron, Ohio, and (II) one from iVlbany, New 

 York. (Specimen No. 53588, U.IS.N.M.): 



Constituents. 



Silica 



Alumina 



Iron sesquioxide 



Lime 



Magnesia 



Alkalies 



Sulphuric acid 



Phosphoric acid 



Carbonic acid and water 



Total 



(I.) 



60. -10 

 10.42 

 5.36 

 9.88 

 4.28 

 0.87 

 0.65 

 0.09 

 8.05 



(II.) 



58.54 

 15.41 

 3.19 

 6.30 

 3.40 

 4.45 

 1.10 



100. 00 



100.47 



The Albany clay is stated hy Nason ^ to glaze at comparatively low 

 temperatures and to rarely crack or check. It occurs in a stratum 4 to 

 5 feet thick. It is used very extensively in the United States, and has 

 even been shipped to Germany and France. (See also Specimens 

 Nos. 53582, U.S.N.M., from Brimfield, Ohio; 53580, U.S.N.M., from 

 Rowley, Michigan, and 52985, 52995, U.S.N.M., from Meissen, Saxony.) 



The name adohe is given to a calcareous clay of a gray-l)rown or 

 yellowish color, very tine grained and porous, which is sufficiently 

 friable to crumble readily in the lingers, and yet has sufficient coher- 

 ency to stand for many years in the form of vertical escarpments, 

 without forming appreciable talus slopes. It is in common use through- 

 out Arizona, New Mexico, and Mexico proper for building material, the 

 dry adobe being tirst mixed with water, pressed in rough rectangular 

 wooden molds some 10 by 18 or more inches and 3 or 4 inches deep, 

 and then dried in the sun. In some cases chopped straw is mixed with 

 it to increase its tenacity. Buildings formed of this material endure for 

 generations and even centuries in these arid climates. The material of 

 the adobe is derived from the waste of the surrounding mountain slopes, 

 the disintegration ])eing mainly mechanical. According to Prof. I. C. 

 Russell it is assorted and spread out over the valley bottoms by ephem- 

 eral streams. It consists of a great variety of minerals, among which 

 (juartz is conspicuous. The chemical nature of the adobes vary widely, 

 as would naturally be expected, and as is shown in the following analyses 

 from Professor Russell's paper: ^ 



^ Forty-seventh Annual Report of the State Geologist of New York, 1893, p. 468. 

 ^ Subaerial Deposits of North America, Geological Magazine, VI, 1889, pp. 289 and 

 342. 



