ANALYSES. 323 



tion products other than as indicated by minute infiltrations of calcite 

 from above. Just above the level of the small creek which flows at the 

 foot of the bluff, at the point indicated by the first series of right-and-left 

 joints near the center of the view, the character of the rock changes quite 

 suddenly, becoming brown and friable, though still retaining its form 

 and easily recognizable granitic appearance. A few feet above, a third 

 zone begins, in which the rock is converted into sand and gravel and 

 which becomes more and more soil-like to the top of the bank, where it 

 becomes admixed with organic matter from the growing plants. The 

 amount of organic matter is alwa3's quite small, however, and in making 

 the analyses care was taken to remove such as was recognizable in the 

 form of rootlets, leaves and twigs. 



Analyses and their Discussion. 



bulk a^-alyses. 



Bulk analyses of each of the three types — (I) fresh gray rock, (II) de- 

 composed l)rown, but still moderately firm and intact rock, and (III) 

 soil — yielded Professor R. L. Packard the results given below : 



I. II. III. 



Ignition 1.22 3.27 4.70 



SiO, 69.33 6G.82 05.69 



TiO, notdet. not det. 0.31 



Al.A 14.33 15.62 15.23 



FeO 3.60 1.69 \ . qq 



FeA 1.88 r ^-'^^ 



CaO 3.21 3.13 2.63 



MgO 2.44 2.76 2.64 



Na,,0 2.70 2.58 2.12 



K2O 2.67 2.04 2.00 



PA 0-10 not det. 0.055 



99.60 99.79 99.765 



It is at once evident from the above that tlie transition from fresh 

 rock to soil lias been brought al^out with very little change in ultimate 

 chemical composition — an assumption of some 3.5 per cent of water, a 

 change of the ferrous oxide to ferric forms, doubtless more or less hy- 

 drated. and a slight decrease in the total amounts of silica, lime, ]>otash 

 and soda being the more conspicuous features. How slight this change 

 lias been is best brought out in the acconi})anying table, in which each 

 analysis is recalculated to a water-free basis. It should be noted, how- 

 ever, that the term water- free, as here used, is not absolutely correct, 

 since the loss on ignition is undoubtedly in part duo to carbonic acid 

 from secondary calcite and organic matter. 



