ANALYSIS OF RESIDUAL SOIL. 



159 



made apparent by the following table, for which, as on previous occa- 

 sions, I am indebted to Dr Milton Whitney, of the Department of Agri- 

 culture. 



Mechanical Analysis of residual Soil. 



Diameter (in millimeters). 



Conventional names. 



(1.) 

 (2.) 

 (3.) 

 (4.) 

 (5.) 



(«.) 



(7.) 

 (8.) 



2-1 



1-.5 



.5-.25 



.25-.1 



.1-.05 



.05-.01 . . . 

 .01-. 005... 

 .005-. 0001. 



Total mineral matter 



(9.) Loss at 110° C 



(10. ) Loss on ignition 



Total 



Fine gravel 



Coarse sand. . . . 

 Medium sand. . 

 Fine sand. . 

 Very fine sand 



Silt." 



Fine silt 



Clay 



Per cent. 



1.15 



2.92 



6.29 



17.42 



15.60 



7.65 



1.83 



35.73 



88.59 

 2.93 

 8.49 



100.01 



Chemical Analyses and their Discussion. 



Below is given the analyses of the fresh rock and residual soil, together 

 with that of the portion decomposed by boiling hydrochloric acid, while 

 in columns 6, 7, and 8 are given calculations from the analyses in columns 

 1 and 3 to show the total loss of material and also the percentage amounts 

 of each of the original chemical constituents saved and lost. These cal- 

 culations, as in previous papers, are made on the assumption that the 

 alumina has remained essentially constant, and though nothing like ab- 

 solute accuracy can be claimed for the results, they are by no means 

 uninteresting and uninstructive. 



The particular features to which attention need here be called are 

 (1) that 30.51 per cent of the fresh rock and 69.18 per cent of the de- 

 composed are soluble in hydrochloric acid and sodium carbonate solu- 

 tions, and that more than half the potash and nearly the same proportion 

 of the soda in the fresh rock is found in the acid extract; (2) that the 

 insoluble portion of the residuary material is mainly in the form of free 

 quartz; (3) that 44.67 per cent of the original matter has been leached 

 away, and that (4) of the original silica, 52.45 per cent is lost, while 

 85.61 per cent of the iron and all the alumina* remain. All the lime 

 has disappeared ; 83.52 per cent of the potash, 95.03 per cent of the soda, 

 and 74.70 per cent of the magnesia. The total amount of water, as indi- 



* This is not absolutely correct, since all the alumina was assumed to have remained in order to 

 give a basis for calculations. 



