74 Scientific Intelligence. 



11. The Educational Series of Rock Specimens collected and 

 distributed by the V. S. Geological Survey ; by J. S. Diller. 

 Bulletin No. 150, U. S. Geol. Surv., Washington, 1898, pp. 400, 

 4.1 pi.; price 25 cts. — A number of years ago the United States 

 Geological Survey undertook the praiseworthy task of collecting 

 and distributing to our leading educational institutions, as an aid 

 in geological teaching, a series of rock collections illustrating the 

 petrology of the United States. Under the able management of 

 Mr. J. S. Diller, aided by many geologists both of the Survey 

 staff and from other portions of the country, this task was 

 sucessfully completed, and about 250 sets, comprising over 150 

 specimens in each, were distributed. In addition, to supplement 

 the value of these collections, the Survey has now issued the 

 volume above mentioned, in which the rocks are described from 

 the standpoint of modern petrography. Under the editorship of 

 Mr. Diller, who also contributes largely to the descriptive 

 matter, the rocks have been described by a number of specialists, 

 in great part those by whom they were collected, and to whom 

 is due our knowledge of the geology of the regions in which they 

 occur. 



The method of classification is simple and rational, and the 

 volume constitutes in fact an excellent practical text-book of 

 petrology for Americans, and as such will be found of very great 

 service to teachers of geology, as well as to those engaged in the 

 more specialized petrographical branches. Its appearance in con- 

 nection with the use of the collections cannot fail to give an 

 impulse to the study of petrography, and the Survey staff in 

 general, and Mr. Diller in particular, deserve great credit for 

 the completion of this useful and public-spirited work. l. v. p. 



12. The Mechanical Composition of Wind Deposits ; by Johan 

 August Udden, pp. 1-69. Augustana Library Publications, No. 

 1. Rock Island, 111., 1898. — The author has carried on a long 

 series of observations in order to show the part played by the air 

 in motion in transporting sand deposits to different distances as 

 determined by their size. Four classes are especially recognized : 

 (1) lag gravels or coarse residue deposits in the rear of sand 

 dunes; (2) drifting sand, constituting the sand dunes of dry and 

 sandy regions; (3) fine sand, soon dropped by the wind in the lee 

 of drifting dunes; (4) atmospheric dust, which only slowly settles 

 out of the air far away from the place where it was raised. 



Many observations in regard to each of these have been made 

 at different points, chiefly in Illinois, Indiana, Nebraska, Kansas 

 and the Dakotas. The results, given in the form of numerous 

 tables, show the percentage of particles of characteristic size 

 present under the given conditions. For example, lag gravels, 

 though varying widely in different localities, include chiefly par- 

 ticles from 4 mm to J mm in diameter ; drift sands those from l mm to 

 i mm ; dune sand is more uniform, from 60 to 70 or 80 per cent of 

 the particles ranging between \ and ^ mm ; lee sand runs down to 

 _yDm or gma u er) an( j atmospheric dust varies from \ to yiF min an( ^ 



