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SCIENCE 



[N. S. Vol. XXVIII. No. 730 



freedom from diseases of the respiratory 

 organs. DiflFerences in food or housing aecom- 

 moderations can not account for the compara- 

 tive freedom of these classes from pulmonary 

 disease." 



The causal relation of foul air to tuber- 

 culosis is shown by the fact that since the 

 British government has payed attention to air 

 space and ventilation the death rate from 

 consumption among the soldiers, sailors and 

 prisoners which was formerly excessive is now 

 considerably less than among the civil popula- 

 tion. 



The dangers of sewer air are being revived 

 again by recent experiments of Horrock's at 

 Gibraltar, which gave results at variance 

 with those obtained by Laws and Andrews. 

 He found that specific bacteria present in 

 sewage may be recovered from the air of 

 drains and sewers, even when the sewage is 

 flowing smoothly and without splashing. He 

 believes that they may be ejected into the 

 air by: (a) the bursting of bubbles at the 

 surface of the sewer, (5) the separation of 

 dried particles from the walls of the sewers 

 and pipes, and probably (c) by the ejection of 

 minute droplets from flowing sewage. 



A similar explanation was offered by Uffel- 

 mann over twenty years ago and Horrock's ex- 

 perimental data, which also showed that the 

 disconnecting trap on a house drain prevents 

 the passage of bacteria present in sewer air 

 into the house drains, will naturally tend to 

 revive the opinion, formerly held, that sewer 

 and drain air may be the means of spreading 

 infectious diseases unless the house drain and 

 fixtures are properly trapped. 



The section oi vitiation of air in industrial 

 occupations is very complete and the table on 

 page 182, giving the comparative mortality 

 figures for males engaged in different dust- 

 inhaling occupations shows conclusively that 

 the hard, sharp and angular fragments of 

 mineral and metallic dust are especially calcu- 

 lated to cause irritation and abrasions of the 

 respiratory passages and thus favor the in- 

 vasion of the tubercle bacillus and also the 

 production of other diseases of the respiratory 

 organs in general. 



The book is accurate and up to date in every 



respect and can be confidently recommended 

 to all interested in hygiene and public health. 

 George M. Kober 



Georgetown University 



Soils and Fertilizers. By Harry Snyder, 

 Professor of Agricultural Chemistry and 

 Soils, University of Minnesota. Third edi- 

 tion. 8vo, 350 pp. New York, The Mac- 

 millan Company. 1908. 

 The first edition of Snyder's book, then en- 

 titled " Chemistry of Soils and Fertilizers," 

 was at the time of its publication in 1899 a 

 most welcome addition to the libraries of 

 teachers of agriculture. It gave in logical 

 and systematic form a brief course in agri- 

 cultural physics and chemistry, and in the 

 practise deducible therefrom, and was widely 

 used in our agricultural colleges by both stu- 

 dents and teachers. But the rapid advance of 

 agricultural science made it advisable to pub- 

 lish a revised second edition in 1905, without, 

 however, materially increasing the length of 

 the text. In the new, third edition we have 

 instead of the 287 pages of the previous edi- 

 tions, 344 pages, slightly smaller than before. 

 The increase is partly due to the addition of 

 illustrations, as in the excellent chapter on 

 laboratory practise, which has been enlarged 

 from 13 to 19 pages, and forms one of the 

 most useful features of the book for the guid- 

 ance of teachers, who often fail to illustrate 

 the facts and principles of their course in a 

 manner both attractive and profitable to their 

 students. Many of these experiments and ap- 

 paratuses are original with Snyder, and very 

 cogent. The twelve pages of review ques- 

 tions, also, are very well calculated to impress 

 upon the student the practical applications of 

 what is brought before him during his course, 

 and to induce attention in advance of the final 

 examination, in place of the " cram " so com- 

 monly indulged in at the end of the session. 



The body of the text itself has been thor- 

 oughly revised so as to include the results of 

 the latest researches in the agricultural field, 

 and one recognizes plainly the ring of the 

 diction of one who knows whereof he speaks 

 from personal investigation. This influence, 

 difficult to define exactly, is nevertheless most 



