August 28, 1908] 



SCIENCE 



111 



important ores, retail prices of cut gems, 

 values of metals and minerals ; then follows 

 an admirable glossary in whicii, however, 

 some of the fundamental terms, such as 

 crystal, mineral and polarize, are not defined 

 with scientific accuracy. 



The tables which follow the index are sum- 

 maries of the descriptions, characters in 

 parallel columns and minerals in order of 

 description. 



The book is of convenient size for the 

 pocket and embodies much easily accessible 

 and useful information. In spite, however, 

 of the fact that it is, as explicitly stated, de- 

 signed for the determination of minerals, its 

 value in the absence of all systematic schemes 

 would seem to be rather to refresh the user's 

 memory as to the characters of known or 

 suspected minerals, than as a guide to the 

 determination of unrecognized material. 



A. J. Moses 



Analysis of Mixed Paints, Color Pigments 

 and Varnishes. By 0. D. Holley, Ph.D., 

 and E. F. Ladd, B.S., Professors of Chem- 

 istry, North Dakota Agricultural College. 

 New York, John Wiley & Sons. Pp. 235. 

 This book presents in a more accessible and 

 considerably enlarged form the results of the 

 work done in connection with the enforcement 

 of the North Dakota paint law. It gives the 

 latest and best methods for the analysis of the 

 substances mentioned in its title, and, what is 

 still more valuable, the composition of these 

 articles as found on the American market. 

 The method for the analysis of linseed oil, 

 however, is incomplete, no mention being 

 made of the process for detecting fish oil in it 

 with certainty. 



Incidentally it furnishes a striking com- 

 mentary on the honesty and integrity of the 

 American paint and oil trade. The authors' 

 investigations showed " white leads " which 

 contained no lead carbonate and but five per 

 cent, of lead sulphate; other pigments were 

 found which were branded in a manner cal- 

 culated to mislead. Not content with this 

 sort of fraud, water, in some cases to the 

 extent of twenty-five per cent., was mixed 

 with the paints and these put up in packages 



which were 10 to 13 per cent, short in weight 

 or measure! The authors have done a real 

 service in showing up such conditions. 



The work is one of the best contributions 

 to the literature of these subjects that have 

 appeared, dealing not only with analyses, but 

 also with specifications, and the application 

 and testing of paints on a large scale, and 

 should be in the library of every one having 

 to do with the subjects treated. 



A. H. Gill 



SPECIAL ARTICLES 



SOME CONDITIONS AFFECTING VOLCANIC ERUP- 

 TIONS 



In the study of such natural phenomena as 

 are difficult to investigate by reason of inac- 

 cessibility, or of danger to the observer, it is 

 natural and often advantageous to consider 

 some analogous, but less obscure phenom- 

 enon and, from a careful study of this, to de- 

 duce the laws which govern the former. A 

 case in point is that of a volcano in eruption 

 which, by its very nature, prohibits close in- 

 spection, but with which a certain degree of 

 parallelism is found in the action of geysers. 

 More than thirty years ago Fuchs called at- 

 tention to the similarity existing between the 

 two, comparing the column of water in the 

 geyser tube to the lava in the interior of a 

 volcano and stating that geysers " ont encore 

 une grande importance en ce sens qu'ils nous 

 permettent de nous faire une idee claire des 

 phenomenes qui produisent les eruptions vol- 

 caniques." (K. Fuchs, "Les volcans et lea 

 tremblements de terre.") In the light of 

 modem volcanological science, however, this 

 generalization of the term "eruptions vol- 

 caniques" will be found too sweeping, for it 

 is clear that the action of a trachytic volcano, 

 whose highly silicious magma is at best in a 

 viscous state, can with difficulty be consid- 

 ered as analogous to that of a geyser where 

 fluidity is the most evident characteristic. 

 A comparative study of the two phenomena 

 should, therefore, be prefaced by the explicit 

 statement that the volcano in consideration 

 is of the basaltic type, with lava which is 

 liquid at the temperature of action, and con- 



