J. Hendiuck and W. G. OctCt 



461 



Differences in origin ami nirthod of formation give rise to differences 

 botli in physical structure and in chemical composition. The differences 

 in physical structure are measured, though only in a crude way, by 

 mechanical analysis, liy which tin' particles of different sizes are 

 separated into arbitrary grcjups. Chemical composition is usually 

 determined by treatment with a conventional strength of acid. For 

 certain purposes these determinations are sufficient, but for a close 

 comparison of soil types much more is needed. Even complete mineral 

 analysis of the whole soil by fusion or treatment with hydroffuoric 

 acid does not help us much. We have endeavoured to gain further 

 information as to the origin and constitution of this soil by subjecting 

 the different mechanical fractions to ultimate analysis and comparing 

 the results with those obtained elsewhere by others. 



Anah/xis of tin' fritcliaus of Craibstone soil. 



A portion of the prepared sample was fractionated by the ordinary 

 method of mechanical analysis, and the fractions, after ignition, analysed 

 by fusion methods. The results are expressed in Table III as per- 

 centages of the relative fractions, and in Table IV as percentages of 

 the total soil. 



Table III. Ullhiiale aiudi/sis of iiiecJiank-al fractions. 

 (Calculated as percentages of dry mineral matter of fractions.) 



Total 



68-01 



11-35 



3-69 



1-81 



0-73 



1-54 



1-54 0-12 88-79 



