43* 



POPULAR SCIENCE MONTHLY. 



SCIENTIFIC LITEKATUEE. 



ENGINEERING. 

 American books on surveying have 

 heretofore been prepared primarily as 

 texts for class use, rather than for the 

 use of the field engineer. This point 

 of view is reversed in the volume of 

 900 pages, by Herbert M. Wilson, en- 

 titled 'Topographic Surveying, includ- 

 ing Geographic, Exploratory and Mili- 

 tary Mapping,' recently issued by John 

 Wiley & Sons. It sets forth, in the 

 main, the practise of the U. S. Geo- 

 logical Survey, and many of the illus- 

 trations have been derived from the 

 publications of that bureau, the col- 

 ored ones being printed from copper 

 plates owned by the Government. 

 Field work, with the plane table, the 

 transit and stadia, the level and 

 office methods of mapping occupy 

 nearly one-half of the volume; about 

 300 pages are devoted to geology and 

 astronomy, and the remainder to pho- 

 tography, camping, and the subsistence 

 and health of field parties. In no book 

 heretofore issued are the practical de- 

 tails of topographic work discussed 

 with such fulness as here, and the 

 numerous tables will be found of great 

 assistance in facilitating computations. 

 Indeed, a special effort seems to have 

 been made in the direction of tables, 

 some of which might well have been 

 omitted; for instance, the space de- 

 voted to the table of Peirce's criterion 

 for the rejection of observations would 

 have been better filled by elementary 

 matter on the method of least squares, 

 and the table for the values of 0.046d, 

 when d=10, 20, 30, etc., seems a re- 

 flection on the mathematical knowledge 

 of the reader. The book is in general 

 clearly written, although the frequent 

 use of italics seems to indicate that the 

 author was often apprehensive that he 



might be misunderstood. It is a valu- 

 able supplement to the text-books of 

 the engineering colleges. 



'Road Making and Maintenance,' 

 by Thomas Aitken (London, Griffin & 

 Co.), deals largely with European prac- 

 tise in street construction. The country 

 roads of England are as a rule better 

 than those of the United States, having 

 been earlier built and more systemat- 

 ically repaired, while great attention 

 is paid to securing uniformity of sur- 

 face. An instrument called the via- 

 graph is described by the author, 

 which takes an automatic record of 

 the inequalities of the street surface 

 and gives the sum of all the vertical 

 depressions found in paving over a 

 mile. A road having 15 feet of such 

 depressions per mile is called excellent, 

 while a fair road has 40 or 50 feet per 

 mile, and a passable one 60 or 80 feet per 

 mile. The cost of this viagraph is 

 moderate, and it is only necessary to 

 drag it along the street in order to 

 obtain the authentic record. It is sur- 

 prising to learn that wooden pavements 

 still continue to be laid in English 

 towns, while brick pavements are prac- 

 tically untried. On questions of city 

 streets American practise seems fully 

 abreast of that of England now that 

 the necessity of good foundations of 

 concrete is fully recognized. *Street 

 Pavements and Paving Materials,' by 

 George W. Tillson (New York, Wiley 

 & Sons), sets forth modern American 

 practise in an exhaustive manner, giving 

 specifications in use in different cities 

 for different kinds of pavements. The 

 first asphalt pavement laid in the 

 United States was in 1870; great diffi- 

 culties were met in adapting asphalt 

 to climate and traffic, but these have 



