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TEE POPULAR SCIENCE MONTHLY. 



field ; to explain the methods of field-work 

 so clearly and minutely that an engineer in 

 practice could, without other instruction, 

 prepare his instruments, and do the work in 

 good shape; and to furnish means of re- 

 ducing the field-notes and methods of plot- 

 ting, the results of many years' experience 

 of many engineers. 



The Lineal Measures of the Semi-civil- 

 ized Nations of Mexico and Central 

 America. By Daniel G. Brinton, M. D. 

 Philadelphia. Pp. 14. 



Dr. Brinton is devoted to the study of 

 the history and civilization of the aborigines 

 of the Americas, and pursues it with indus- 

 try in all its branches. In the present mon- 

 ograph he gives the results of his analyses 

 of the words for weights and measures in 

 the Maya, Cakchiquel, and Nahuatl or Az- 

 tec languages, instituted to ascertain, if 

 possible, what units, if any, were employed 

 by the peoples who spoke them. The meas- 

 ures of these nations seem to have been de- 

 rived from the body, and some of them were 

 curious. A unit of land-measure among 

 the Cakchiquels was the circumference of 

 the human figure. A man stood erect, his 

 feet together, and both arms extended. The 

 end of a rope was placed nnder his feet and 

 its slack placed over one hand, then on 

 top of his head, then over the other hand, 

 and was finally brought to touch the begin- 

 ning. This gave somewhat less than three 

 times the height. The Aztecs had four 

 measures from the point of the elbow : one 

 to the wrist of the same arm, a second to 

 the wrist of the opposite arm, a third to the 

 ends of the fingers of the same arm, and the 

 fourth to the ends of the fingers of the op- 

 posite arm. Neither of the three nations 

 was acquainted with a system of estimation 

 by weight, or with the use of the plumb- 

 line, nor with an accurate measure of long 

 distances. 



The Magnetism of Iron and Steel Ships. 

 An Explanation of the Various Ways in 

 which it affects the Compass. By T. A. 

 Lyons. Washington : Government Print- 

 ing-Office. Pp. 124, with Plates. 



This volume is the seventeenth of the 

 series of " Naval Professional Papers." Its 

 purpose is to exhibit in a concise form the 

 principal phenomena of the deviations of 



the compass on iron ships. First are de- 

 scribed the characteristics of a steel mag- 

 net, the method of determining those char- 

 acteristics for any particular one, and the 

 reciprocal action of two magnets. Next, the 

 similitude of the magnetism in an iron or 

 steel ship to that of an ordinary bar magnet 

 is established, and the inquiry is made ap- 

 plicable to the ship, whereby we may be- 

 come acquainted with her magnetic pecul- 

 iarities. These observations are comple- 

 mented by a number of experiments, all 

 helping to complete the investigation, and 

 to bring out a more satisfactory elucidation 

 of the subject. 



The Religion of Philosophy ; or, The Uni- 

 fication of Knowledge. A Comparison 

 of the Chief Philosophical and Religious 

 Systems of the World, made with a View 

 to reducing the Categories of Thought, 

 or the most General Terms of Existence, 

 to a Single Principle, thereby establishing 

 a True Conception of God. By Raymond 

 S. Perrin. New York : G. P. Putnam's 

 Sons. Pp. 566. Price, $4. 

 The purpose and character of this elabo- 

 rate volume are admirably summed up in its 

 comprehensive title-page. The author has 

 taken to metaphysics from the most modern 

 point of view, and labored with great assi- 

 duity, much learning, and no little analytic 

 and constructive skill, to work out the grand 

 conception of unity in the world of philo- 

 sophical thought. Firmly accepting that 

 important principle of science, that the few- 

 er assumptions we make in the explanation 

 of things the better, he has labored to re- 

 duce the number of principles hitherto postu- 

 lated as the primary elements of existence, 

 and to show that there is but one final and 

 universal principle, of which all others are 

 but derivative expressions. Part I, consist- 

 ing of eight chapters, is an epitome of the 

 history of philosophy from the dawn of spec- 

 ulation among the Greeks down to the eclec- 

 ticism and positive philosophy of France and 

 the Scotch school. The contributions of the 

 most illustrious philosophers embraced in 

 that long period are sifted and estimated 

 with a view to their bearings upon the fun- 

 damental proposition which the author finds 

 himself called upon to establish. Part II 

 consists of eight chapters, devoted to " The 

 Nature of Perception," four of which are 

 given to Herbert Spencer and four to G. H. 



