Supplement to "Nature" November 6, 1902. 



Vll 



It was found, according to Mr. Whitney's preliminary 

 review, 



' that it was quite possible to map these soil areas in- 

 dependently of the geology of the area, or the exact 

 chemical or physical character of the soil ; that the 

 proper course was to construct maps in the field, showing 

 the area and distribution of the soil types ; to explain as 

 fully as possible from geological considerations the origin 

 of the soil and to leave the soil chemist and physicist 

 study the differences. The fact is recognised that these 

 chemical and physical properties of soils are so com- 

 plex and difficult that it may take many years to explain 

 them through laboratory investigation ; but, pending this 

 complete investigation, the maps themselves will be of 

 the utmost value to agriculturists in indicating the areas 

 over which certain soil conditions are found to prevail. 

 . . . The recent successful growing of Sumatra tobacco 

 on a certain soil in the Connecticut Valley is a very 

 striking instance of the possibilities growing out of the 

 detailed soil survey in any given locality." 



The whole work is an excellent example of the thorough- 

 ness with which America carries out her State services ; 

 the maps themselves are clear and distinct ; some of them, 

 like the Saint Ana (California) sheet, represent a very 

 complex distribution of soils, the survey of which must 

 have involved no light amount of field work, while the 

 accompanying text is most liberally illustrated with 

 analyses, sketch maps and sections, and photographs 

 illustrative of scenery, crops or vegetation, the ease with 

 which photographic illustrations are now produced being 

 perhaps responsible for the trivial nature of one or two of 

 the objects selected. 



Several of the sections of the survey deal with that inter- 

 esting factor in all arid or semi-arid areas, the existence of 

 alkali soils and their extension under irrigation, which is, 

 unfortunately, almost the only method of farming possible. 

 Alkali is used in a generalised sense as indicating any 

 predominance of soluble salts, generally sulphates and 

 chlorides of sodium, magnesium and calcium, in the 

 ground water, so that vegetation is destroyed or restricted 

 to certain "salt" plants, and on occasion the salts 

 effloresce in a white powder on the surface. Sometimes 

 carbonates of the alkalis are also present, which by their 

 injurious action upon the texture of the soil and their 

 solution of the humic acids give rise to " black alkali " 

 spots, more dreaded even than the white. These " alkalis " 

 probably represent nothing more than the normal products 

 of the weathering of the fundamental rock minerals, 

 but owing to the limited rainfall there is no perco- 

 lation through soil and subsoil, to wash everything 

 soluble into the rivers. Instead the salts remain in the 

 subsoil, and irrigation, by raising the level of the ground 

 water, may easily bring the salts so near the surface that 

 they rise in the capillary water to the surface and there 

 are crystallised out. An instance of the damage due to 

 careless irrigation and the rise of the subsoil water is 

 given in the report before us in the account of the Salt 

 River Valley, Arizona. 



The phenomena of alkali soils and their increase 

 through irrigation are neither new nor confined to the 

 I'nited States; any arid climate where the products of 

 weathering are not removed in the "country drainage" 

 shows the same problem. Uur irrigation engineers 

 in India and Egypt are regularly confronted with the 

 problem, for which there is only one solution, under- 

 NO. I/23, VOL. 67] 



drainage so that the cultivated soil may be washed from 

 time to time, and careful cultivation to minimise all 

 evaporation from the soil except through the leaves of 

 the crop. But though the " alkali " problems are common 

 in the old world, it has not been until the time of 

 Hilgard, Whitney and the present Division of Soils in the 

 U.S. Department of Agriculture that we have had any 

 real knowledge of their composition, or any study of the 

 physical and chemical principles underlying the move- 

 ment of the injurious material in the soil. 



The character of the information provided by a soil 

 survey must largely depend upon the nature of the 

 country ; in many parts of the United States agriculture 

 is so recent that there is no accumulation of experience 

 as to suitable crops, hence the survey, by comparison of 

 the texture of the soil, the climatic features, depth to 

 ground water, &c, with the conditions prevailing in known 

 areas, can directly advise the settler with what crops he 

 is most likely to succeed. 



But in a country like our own, the land has been under 

 cultivation so long that a great mass of local information, 

 based upon experience, exists as to the character even of 

 individual fields. Hints as to methods of cultivation or 

 cropping based upon analysis are likely to be too general 

 to be of any service ; the chief application is rather the 

 information that can be afforded as to the use of manures, 

 for enormous economies could still be effected in the 

 manure bill of nearly every farmer who buys artificial 

 manures, if they were properly adapted to his soils and 

 crops. 



In Britain, the great initial want is the publication Oi 

 drift maps of the Geological Survey on the six-inch-to-the- 

 mile scale ; were this in existence, it could be rapidly 

 supplemented by the work of the local agricultural col- 

 leges until every farmer could be put in possession of that 

 exact knowledge of his soil which is fundamental for all 

 farming operations. A. D. H. 



AN ADVANCED TEXT-BOOK OF BOTANY. 

 A University Textbook of Botany. By Douglas 

 Houghton Campbell, Ph.D. Pp. xv + 57c). (New 

 York : The Macmillan Company ; London : Macmillan 

 and Cc, Ltd.) Price 175. net. 



THERE are probably few books that are much harder 

 to write than those which endeavour to deal, within 

 a limited space, and from the point of view of the needs 

 of the advanced student, with the whole range of any 

 extensive branch of science. And indeed it is perhaps 

 doubtful whether the time has not gone by when such 

 works can hope to lay claims to much educational utility. 

 Certainly this is the case as regards botany, which now 

 covers so wide an area of knowledge that a bulky volume 

 would be required merely to indicate in outline the more 

 salient facts and their general connections and bearings. 



The impression seems to be gaining ground that, for 

 students of university type at least, a better method of 

 treatment lies in the endeavour to expound on more 

 truly scientific lines the facts embraced in its smaller 

 subdivisions rather than in an attempt to range over the 

 whole science in the course of a few hundred pages. 

 And we think this modern tendency is a good one. The 

 student who is hurried over so large a field of knowledge 



