September 3, 19 14] 



NATURE 



cises. Altog^ether the book is one that the teacher 

 may use with great advantage and in the certainty 

 of getting much help in devising useful courses 

 for his classes. 



(3) The third book is by Prof. Wheeler who 

 was long director of the Agricultural Experiment 

 Station of Rhode Island, and then became chem- 

 ical expert to the .American Agricultural Chemical 

 Company. His book deals exclusively with 

 manures and fertilisers, and is therefore more 

 specialised than the volume just referred to. A 

 very interesting account is given of the subject, 

 indeed, we know of no American publication that 

 deals better with it. The author has rightly 

 made liberal use of the admirable series of in- 

 vestigations conducted at Rhode Island during 

 the term of his directorship, and in particular 

 goes very fully into the question of liming. Some 

 remarkable observations were begun in 1890 at 

 Rhode Island and it was found that sulphate of 

 ammonia was highly toxic on certain soils, even 

 in the first season of its application. Experiments 

 soon showed that this effect was due to the pro- 

 duction of acid conditions in the soil, which could 

 be corrected by sodium carbonate, potassium 

 carbonate, calcium carbonate, but not by chlor- 

 ides or sulphates. Liming- was therefore indicated 

 as the proper method of dealing with the trouble. 

 These observations appear to have been the first 

 that were made on the subject ; and they lead to 

 a very complete study of the method of correcting 

 acidity arising from the use of ammonium 

 sulphate. 



A further interesting feature is the prominence 

 given to the use of seaweed as a manure. This 

 subject attracts periodical attention, but very little 

 progress has been made in the direction of utilisa- 

 tion, in spite of the enormous possibilities it seems 

 to present. And yet the amount of fertilising 

 material thrown up on our shores in the course of 

 a year is enormous. 



\ pleasant feature of the book is the great pro- 

 minence given to European work, Rothamsted 

 experiments in particular coming in for a great 

 amount of attention. 



The book is very interesting and will be of 

 considerable value to teachers and students of 

 the subject. E. J. Russell. 



OUR BOOKSHELF. 

 Morocco the Piquant, or Life in Sunset Land. By 

 G. E. Holt. Pp. xi + 242. (London: \Vm. 

 Heinemann, 1914.) Price 65. net. 

 Mr. Holt, who seems to have held for about six 

 years the post of American vice- and deputv- 

 consul-general at Tangier, enjoyed facilities of e>> 

 ploring the interior of Morocco denied to European 

 NO, 2340, VOL. 94I 



diplomatists who exercise a more active and less 

 disinterested influence on the affairs of that dis- 

 tracted country. The note of his book is the 

 strange conflict of Oriental and Western culture 

 so close to Europe. He gives in naive fashion 

 and with a breezy style a sketch of the cosmo- 

 politan popul^ion of Tangier, where he is re- 

 minded everywhere of the Arabian Nights. He 

 was able to visit that strange Alsatia within ten 

 miles of Tangier, held by the turbulent Angheras ; 

 he interviewed the bandit Raisuli, whom the 

 Spaniards, it is said, are now ready to take into 

 their service, at his refuge Arzila. 



Perhaps the best part of the book is the chapter 

 describing the Djinn, or evil spirits, the primitive 

 animistic belief over which Islam is only a veneer, 

 and his visit to a peasant household, an indus- 

 trious farmer and his capable wife, good speci- 

 mens of the fine material in the population, and 

 capable of regenerating this harassed land if only 

 it were subjected to a decently efficient Govern- 

 ment. .A.n energetic observer, with his American 

 ideas of hustle and the superiority oi Western 

 industrialism is not the best authority on a 

 primitive culture like that of Morocco, and his 

 observations do not go far beneath the surface. 

 But the facts of the present system and the notes 

 on popular superstitions will interest students of 

 politics and folklore. In face of the recent defeat 

 of the Senoussi by the Italians, we can scarcely 

 accept the prediction that Europe is menaced by 

 a Mohammedan rising' in North Africa. 



Elementary Logic. By A. Sidgwick. Pp. x-r250. 



(Cambridge L'niversity Press, 1914-) Price 



35. 6d. net. 

 Ax excellent manual, combining- an adequate 

 account of the old logic with a good exp)osition of 

 modern developments. As becomes a logician, 

 Mr. Sidgwick divides his book into parts and 

 smaller sections, with admirable system and 

 sequence. Part i. deals with the syllogism in all 

 its forms, also with induction and fallacies, in 

 which matters the author follows Mill for the most 

 part. Interesting illustrations are chosen, and 

 the treatment renders the text as readable as 

 circumstances allow. It is adm-ttedly impossible 

 to make " Barbara " and her associates look any- 

 thing but dull, however they are dressed up ; but 

 logic (as Browning said of his own poetry) is 

 "not a substitute for dominoes," so the student 

 will no doubt struggle through. Mr, Sidgfwick 

 gets the dull part disposed of as quickly as 

 thoroughness will allow. In Part ii. we reach the 

 more interesting and " live " part. The modern 

 point of view is adopted, and formal logic is 

 shown to establish only validity and not truth, 

 because there is always something assumed. 

 Further, classes are man-made, not nature-made ; 

 and, as we cannot say all that can be said about 

 5, S may be in one class in certain of its relations, 

 and in another when others of its aspects are 

 being considered. Briefly, truth is relative to pur- 

 pose. And proof is never coercive. The new 

 logical method is modest. It looks forward with 

 confidence, however, to a "great increase in the 



