562 



THE POPULAR SCIENCE MONTHLY. 



expressing it. He treats also of that exag- 

 geration of spontaneous attention known as 

 surprise or astonishment. The chapter up- 

 on voluntary attention makes up the greater 

 portion of the volume. The study of nat- 

 ural attention enables him to inquire into 

 the genesis and mechanism of voluntary at- 

 tention, and to arrive at some comprehen- 

 sion of it. He concludes the chapter with 

 the statement that attention in no respect 

 resembles an independent activity; that it 

 is bound up with perfectly determined phys- 

 ical conditions, that it acts only through the 

 latter, and is dependent on the same. The 

 last chapter treats of morbid states of at- 

 tention. The name of the author is a guar- 

 antee that the work is both interesting and 

 instructive. 



A System of Inorganic Chemistry. By 

 William Ramsay, F. R. S., Professor of 

 Chemistry in University College, Lon- 

 don. Philadelphia : P. Blakiston, Son 

 & Co. Pp. 700. Price, $4.50. 



The word " System " in the above title 

 has especial significance. It indicates that 

 the treatise to which it is applied is charac- 

 terized by a methodical arrangement. Tak- 

 ing the periodic classification of the elements 

 as a basis, the author has undertaken to bring 

 into the field of inorganic chemistry an order- 

 ly arrangement similar to that which has pre- 

 vailed for more than twenty years among the 

 compounds of carbon. This, he says, owing 

 to traditional and commercial influences, has 

 not been done before in any book written in 

 English. After a short historical introduc- 

 tion the elements are considered in order, 

 and within a moderate compass. Next their 

 compounds with the halogens are taken up. 

 The author names as a defect of many previ- 

 ous books the ignoring of the double halides, 

 except in a few special instances ; accord- 

 ingly, he has taken pains to have these com- 

 pounds well represented. The oxides, sul- 

 phides, selenides, and tellurides follow next, 

 " double oxides, such as sulphates, for exam- 

 ple, being considered among the compounds 

 of the simple oxides with the oxides of other 

 elements." Other features of previous books 

 which Prof. Ramsay has aimed to avoid are 

 magnifying the difference and obscuring the 

 relationship between acid hydroxides and 

 basic hydroxides, neglecting the borides, 



nitrides, etc., and giving pre-eminence to 

 methods of preparing compounds which are 

 of commercial utility over other methods 

 which have fully as much scientific impor- 

 tance. After the account of the oxides, a 

 few chapters are occupied with the borides, 

 carbides, and silicides, and the nitrides, phos- 

 phides, arsenides, and antimonides ; and in 

 these the organo-metallic compounds, the 

 double compounds of ammonia, and the 

 cyanides are considered ; while a short ac- 

 count is given of alloys and amalgams. 

 " The chemistry of the rare earths, which 

 must at present be relegated to a suspense 

 account, is treated along with spectrum anal- 

 ysis in a special chapter ; and the system- 

 atic portion of the book concludes with an 

 account of the periodic table." The con- 

 cluding part of the volume deals with man- 

 ufacturing processes, which are so grouped 

 that substances generally manufactured un- 

 der one roof are treated together. In re- 

 gard to the adaptability of his system to 

 teaching the author says : " Having used it 

 for four years, I am perfectly satisfied with 

 the results. For the student, memory work 

 is lightened; for the teacher, the long, te- 

 dious description of metals and their salts 

 is avoided ; and I have found that the stu- 

 dent's interest is retained, owing to the fact 

 that all the ' fire-works ' are not displayed at 

 the beginning of the course, but are distrib- 

 uted pretty evenly throughout." 



The Iron Ores of Minnesota. By N. H. 

 Winchell (State Geologist) and H. V. 

 Winchell. Minneapolis : The Geologi- 

 cal and Natural History Survey of Min- 

 nesota. Pp. 430. 



This extended and practical book is due 

 to a State law directing the Geologist to make 

 examinations and reports in regard to eco- 

 nomic products. The first part of the vol- 

 ume describes the distribution and geology 

 of the iron ores of Minnesota so far as they 

 are known. These comprise magnetites, 

 hematites, and some limonites. Next the 

 methods of exploration and mining that are 

 employed in the State are described, and 

 accounts are given of the principal mines. 

 There is a chapter on the facilities for trans- 

 porting and marketing the Minnesota ores, 

 another on the origin of the deposits de- 

 scribed in the first part of the report, and a 



