408 SECTIONAL TRANSACTIONS.— M. 



For small areas, such as an experimental farm, where the parent material may be 

 the same throughout, and where configuration and micro relief are very important, 

 the dynamometer affords a useful method of surveying the soil. 



Continents give the widest scope for the surveyor, for here all groups of soil are 

 found ; the great climatic zones form the first great groups, within these come 

 divisions based on the nature of the parent material, and within these again the 

 smaller divisions based on local sorting out of soil materials resulting from con- 

 figuration of the land ; finally, there come the subdivisions due to the micro relief. 



Prof. G. W. Robinson. — -From the standpoint of the practical soil surveyor, the 

 present question dates from the pioneer work of Sir A. D. Hall and Sir E. J. Russell 

 in Kent, Surrey and Sussex. In their survey, soils were classified according to their 

 parent geological formation. The geological map, with certain adjustments, was 

 also the soil map. Various soil surveys have been executed since the publication of 

 Hall and Russell's work, and it has been found that the geological classification of 

 soils is not always applicable. Considerable interest has been aroused in the Russian 

 work on soil classification, but although we have learnt the importance of profile 

 studies, we cannot entirely adopt the Russian system as applicable to this country. 

 For the present, our task is to collect important data such as surface, relief, texture, 

 water conditions, colour and stoniness. Above all, profile descriptions are required. 

 While a soil map based on profile would be very valuable, since profile is the 

 summation of the effect of a number of factors each of which can operate in a number 

 of different ways, the number of kinds of profiles is likely to be too large for practicable 

 mapping. It might be better in generalising from the 6" field maps, on which all data 

 are recorded, to make more than one 1" map. For example, one map might show 

 the nature of the parent material, another the texture of the surface soil, and a third 

 the character of the drainage conditions. For the present, our task is to collect 

 data and to generalise from these data in such a way as to bring together into classes 

 those soils which are most nearly alike, leaving for the future the work of synthesising 

 those regional classifications into a more comprehensive scheme. 



Prof. J. Hendrick. — There are at present considerable differences of opinion in 

 this country as to the methods of soil survey and mapping. The importance of 

 uniformity was emphasised. The soil maps of a country should all be prepared on a 

 uniform system or else their usefulness is greatly diminished. 



There are three great factors on which the nature of a soil depends : ( 1 ) the 

 materials from which it is derived, the rocks and organic materials from which it has 

 been formed ; (2) the climate in which it was formed ; and (3) the topography of the 

 place where it was formed. The vegetation does not form an independent factor, as 

 it depends on the other three and in turn reacts upon the nature of the soil. All of 

 these factors have long been recognised, but we have in recent times made much 

 advance in our knowledge of their action, and have in particular learnt much about 

 the climatic factor. We have also learnt that the resultant of all these factors is 

 expressed in the soil profile. The modern views of soil profile are only a development 

 of the earlier division of the subject into soil and subsoil. As the profile expresses the 

 result of all the soil-forming agencies, the best method of mapping soils is in terms of 

 profiles. We require to get busy and collect and tabulate accurately the facts as to 

 soil profiles ; when we have collected a sufficient body of facts they will require to be 

 classified and the result expressed by means of soil maps. As knowledge accumulates, 

 the value of such maps will ever increase. 



Prof. N. M. Comber. — Surveying and mapping soils on the basis of the soil profile 

 has two important characteristics. 



(1) It considers the soil as a whole. — No other process of classification does this. 

 It is frequently said, referring to a particular area, that the soil has a certain 

 mechanical composition, which statement implies that the mechanical analysis of the 

 soil is uniform throughout its depth. Except in the case of certain new warp soils 

 this is probably never true. The study of the profile differentiates between the texture 

 factors of different horizons. The same consideration applies to any other character- 

 istic which may be studied separately in each horizon. 



(2) It takes cognisance of the soil- formation 2)rocesses. — The processes going on in 

 a soil effect removals, leaehings and depositions and the soil profile reflects these 

 processes. The importance of 'this cannot be exaggerated, for it is a philosophical 

 necessity that one cannot claim a scientific knowledge of soil without a knowledge 

 and understanding of what has gone on in its formation, and what is still going on 



