426 Soientijic Intelligence. 



technical ciifjineer who has made a special study of the glass 

 industry. Mr. Frink believes that it was an error to attribute 

 the specimen figured in A of the plate to simple flowage. He 

 sends a specimen whicii closely resembles it and says that these 

 can be produced at will in the flattening ovens by laying sheets 

 of glass one upon the other and submitting them to the action of 

 heat for varying periods of time, and the longer the time the 

 more opaque the mass will become. The latter statement refers 

 to the greater number of minute spherulites. The specimen 

 shows that the glass plates have been softened to a viscous 

 condition, from the bent and wavy layers they present, and are 

 completely welded. The plane of each two contiguous surfaces 

 is marked by a white film composed of innumerable minute, white 

 spherulites separated by clear green glass. In explanation of 

 this it has been suggested to the writer that the film of air 

 between the plates may have helped in the process. This seepas 

 quite possible, for as the glass softened, the gas may have ren- 

 dered this layer less viscous, by entering into the molten solution, 

 to the degree where crystallization could take place, while the 

 intermediate layers were too viscous to permit of this. With 

 respect to the specimen of Kane glass figured, it may be then, as 

 Mr. Frink suggests, that it was not formed by actual flowage. 

 A possible explanation for it may be that it represents successive 

 droppings of portions of melted glass from the broken furnace 

 upon one another, which flattened down, and along whose flat- 

 tened surfaces the films of spherulites developed. It appears too 

 thick and irregular to have been made purposely, as suggested by 

 Mr. Frink. 



In regard to the formation of spherulites in glass Mr. Frink 

 says that he thinks that the difference in specific gravity between 

 them and the glass is too slight to condition their arrangement, 

 and that this is chiefly due to the viscosity, temperature, and 

 flow of the glass. Sometimes they are at, or near, the surface ; 

 sometimes 12 or 18 inches below it there will be a stratum con- 

 taining innumerable numbers of them. In general, the deeper 

 ones are of larger dimensions. He regards them as being formed 

 at the line of " mean flow," which may perhaps indicate one 

 where the conditions are right for crystallization, being neither 

 too hot on the one hand, nor too stiff and viscous on the other. 



L. V. PIRSSON'. 



17. Economic Geology ; by Heineich Ries. 3d edition. Pp. 

 589, 237 figs., 56 pis. New York (The Macmillan Company). — 

 This work, originally published in 1905, has already gone through 

 two editions and firmly established itself as a text-book of its 

 subject. The book, in the present edition, has been revised and 

 considerably amplified in scope and size. While its general 

 arrangement remains the same, much more space has been devoted 

 to the detailed description of the individual mineral districts. 

 The number of the text illustrations has been increased nearly 

 three times, while the number of the plates has been more than 

 doubled. w. e. p. 



