BISSKI-L] 



ARTIFACTS 



U^} 



Tlio process is well illustrated in plate xvi, h." 



Another woll-known clay pit is situated on MeClellen's branch, at 

 the northeastern base of the Saoaton hills (])1. xvi, c), whence a 

 whitish clay is obtained. The villages about the Casa Blanca ruin 

 ol)tain elay from pits within a stone's throw of the ruin itself and 

 from the river bottom near the village of Kso'tuk. 



The tempering materials used in the clays last mentioned are sand 

 and ground potsherds. The clay from the Skftsfiwallk hills is so 

 coarse that it requires no tempering. 



Red ocher is employed as a slip, which is applied to the surface of 

 the common utensils just before the drying that precedes burning. 

 The water coolers are u.sually made without this coating of ocher. 



Black gum is used for decoration. Tills Is obtained by boiling in 

 a small earthen pot, or in a segment of a large one, mesquite chips 



a Samples of this clay were submit ted toDoctor Wiley, Chief of the Bureau of Chemistrj- of the Depart- 

 ment of Agriculture, who ascertained the percentage composition of the material to be as follows; 



Per cent 

 Combined water, organic matter, and other 



volatile constituents (loss on ignition). . . 4. 94 



Sulphuric acid, SO3 4,'* 



Carbon dioxide, COj Trace 



99.90 



Per cent 



Silica, SiOa 59. 64 



Alumina, .VlsOa 18. 55 



Ferric oxide, FejOj 6. 72 



Manganous oxide, MnO Trace 



Lime, CaO 2.35 



Magnesia, MgO 1. 44 



Alkalies, K2O and NajO 5. 81 



He also explains the general method of determination. 



For industrial purposes an attempt is made to separate the proximate constituents of a elay by 

 what is Killed a ■■ rational analysis." For this purpose the clay is treated with sulphuric acid, which 

 is supposed to dissolve the clay substance proper and leave insoluble quartz sand and sand composed 

 of feldspar or other minerals. 



In order that the composition of this clay might be compared with analyses of other clays made upon 



this plan, a detennination was made of the matter insoluble in sulphuric acid in sample 248S1, with the 



following results: 



Per cent 



Clay substance 35. 33 



Quart?, sand, feldspathic detritus, etc .' 04.57 



99.90 

 The sand insoluble in sulphuric acid is composed approximately as follows: 



Per cent 



Feldspathic detritus, etc 28. 57 



Quartz sand 36. 00 



Comparison of these results with analyses given by Langenbeck indicate that the material represented 

 by sample 24.SSI resembles the clays used for the production of so-called " reel ware" mon' than any 

 other class of clays use<l in pottery manufacture by civilized peoples. The following analysis of a 

 typical clay used for making '• red wan'" is quoted from Langenbeck for purposes of comparison (The 

 Chemistry of I'ottery, 1895. (30): 



Total analysis 



Per cent 



Silica 74.75 



Alumina 12. 55 



Ferric oxide 5.28 



Lime 1.28 



Magnesia 85 



Alkalies 2. 27 



Combined water 3. 23 



ica21 



national analysis 



Per cent 



Clay substance 39. 12 



Quartz 52. 54 



Feldspathic detritus 8. 55 



ion. 21 



