328 



SCIENCE 



[N. S. Vol. XXXIX. No. 1000 



gradual, rather than forced, improvement in 

 the milk supply, and sanitarians are warned 

 against entertaining premature conclusions. 

 Those sanitarians who have recklessly con- 

 nected mastitis in cows with human diseases 

 receive criticism from the author, although he 

 does not neglect to emphasize that milk from 

 cows with diseased udders should be rigor- 

 ously excluded from human consumption, un- 

 less previously boiled. The author also points 

 out that — as desirable as it is to establish 

 grades of market milk — existing regulations 

 are rarely reasonable and generally immature. 

 Numbers of bacteria in milk are of relatively 

 smaller significance than the possible presence 

 of pathogenic bacteria. These may multiply 

 in milk of small bacterial content more rapidly 

 than in milk rich in bacterial life. Special 

 emphasis is laid on the necessity of instructing 

 producers. And here it must be stated that 

 Professor Lohnis ranks among those old-world 

 scientists who are ready to give full credit to 

 American workers in agricultural fields. 



One lecture is devoted to the bacteriology 

 of butter and two lectures to cheese. There 

 are five lectures on the bacteriology of manure 

 and soil. These are also conservative and 

 critical. Finally, the whole subject is re- 

 viewed in a retrospect and a prospect. Valu- 

 able suggestions for those interested in re- 

 search work in agricultural lines are given. 



As a whole the subject-matter is presented 

 in good style, the numerous illustrations are 

 exceptionally clear, and no one can read the 

 book without adding materially to his knowl- 

 edge and broadening his views. 



P. G. Heinemann 



Franz von Kohells Lehrhuch der Mineralogie. 



Seventh edition. By K. Oebbeke and E. 



Weinschenk. Leipzig, Friedrieh Brand- 



stetter. 1913. Pp. viii + 405 ; 1 plate ; 344 



figures in text. Price, 8.50 Marks. 



In 1899 the sixth edition of this popular 



German text-book on mineralogy appeared 



under the same joint authorship as the present 



edition. In the new edition the text has been 



increased by 67 pages. The general portion 



has been entirely rewritten and the descriptive 



part revised so as to bring the mineral data 

 up to date. 



There are three subdivisions in the general 

 part, namely: (1) Crystallography, (2) Phys- 

 ical Mineralogy, and (3) Chemical Mineral- 

 ogy; the special part is devoted to Descriptive 

 Mineralogy. 



Crystallography is discussed in 70 pages 

 and under three headings, (a) general morph- 

 ological properties of minerals, (6) special 

 geometrical properties of crystals and (c) 

 twins, development and intergrowths of min- 

 erals and inclusions. The discussion of cry- 

 stallography is well adapted to the needs of 

 the beginning student. The more important 

 classes of crystals are considered at length 

 upon the modern basis of symmetry, but refer- 

 ence is also made to the rather useful ideas 

 from the standpoint of pedagogy of holohed- 

 rism, hemihedrism and so forth. The crystal 

 drawings are exceptionally clear. Fig. 51 is, 

 however, inverted. 



Thirty-seven pages are devoted to physical 

 mineralogy, which includes the following 

 subdivisions, (a) specific gravity, (&) elastic- 

 ity and cohesion, (c) optical properties and 

 {d) miscellaneous physical properties. The 

 discussions in this section are again limited 

 to only that which is of importance to the stu- 

 dent who has a general knowledge of mineral- 

 ogy in mind. Thus, the polarization phenom- 

 ena of crystals are disposed of in 14 pages. 



The next 60 pages are devoted to chemical 

 mineralogy. Here, (a) general chemical prop- 

 erties, (6) occurrence and formation, (c) 

 weathering and decomposition, {d) synthesis 

 and (e) classification and nomenclature of 

 minerals are discussed. The chapter on the oc- 

 currence and formation of minerals contains 

 a large amount of information not usually in- 

 cluded in text-books on mineralogy of this 

 character. Brief reference is first made to the 

 classification, form, structure and paragenesis 

 of mineral deposits. Then follow concise de- 

 scriptions of the various types of the more im- 

 portant rocks and mineral deposits. This 

 chapter is very well written, and similar dis- 

 cussions could be introduced to advantage in 

 American texts on mineralogy. 



