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POPULAR SCIENCE MONTHLY. 



Prof. A. Afilnes Marshall's monograph on 

 The Frog, intended as an introduction to 

 anatomy, histology, and embryology, was 

 written to guide and direct the student 

 through the practical part of this work, 

 and met a want the whole ground of which 

 was not covered by any manual existing at 

 the time of the original publication. It gives, 

 in the introduction, practical instruction in 

 the methods employed in biological investi- 

 gation ; followed by the application of these 

 methods to the anatomical and histological 

 examination of the animal ; the frog being 

 selected because it is easy to get and con- 

 venient to dissect, and is a fairly typical ex- 

 ample of the group of vertebrates. The 

 preparation of the present, the fifth, edition 

 was Prof. Marshall's last professional act, 

 and was completed only a week before his 

 death. (Manchester and London : Smith, 

 Elder & Co. New York: Putnams, $1.40.) 



An Elementary Text-book of Mechanics, 

 by R. T. Glazebrook, is the latest of the Cam- 

 bridge Natural Science Manuals to reach us. 

 The most satisfactory method of teaching 

 the natural sciences is by means of experi- 

 ments which can be performed by the 

 learners themselves. This book consists of 

 a series of such experiments which have 

 been used by the author in teaching his 

 classes ; the experiments are followed by an 

 explanation and an account of the deductions 

 to be drawn from them. (Macmillan, $1.26.) 



Imagination in Dreams, by Frederick 

 Greenwood (Macmillan & Co., $1.75), treats 

 of a subject with which most of us are fa- 

 miliar through personal experience. Two 

 essays, previously published in English peri- 

 odicals, form the foundation for the work, 

 which as a whole is a rather unscientific dis- 

 cussion of curious psychic phenomena, which 

 are in many cases closely allied, and depend- 

 ent on morbid and diseased conditions of 

 body and mipd, and very probably have little 

 value hi determining the normal working of 

 the brain. A number of queer dreams are 

 detailed, many of them the author's own 

 products. He thinks that the limits general- 

 ly set for the imagination are at times over- 

 leaped in sleep and that " some dream visions 

 are creations of the mind." 



Volume XXXII, Part I, of the Annals 

 of the Astronomical Observatory of Harvard 

 College contains an interesting statement of 



the methods in astronomical photography 

 followed at the Harvard Observatory. There 

 are also two chapters giving the results of 

 researches by Prof. William H. Pickering on 

 the Great Nebula in Orion and on the lunar 

 surface. The former was conducted exclu- 

 sively by photography while the latter em- 

 braced both visual and photographic obser- 

 vations. 



Part I of Volume III of the final report 

 on the Geology of Minnesota is devoted to 

 paleontology, and is made up of contributions 

 by Leo Lesquereux, Anthony Woodward, 

 Benjamin W. Thomas, Charles Schuchert, 

 Edward 0. Ulrich, and Newton H. Winchell. 

 Prefixed to the special monographs which it 

 contains is a historical sketch of investiga- 

 tion of the Lower Silurian in the upper Mis- 

 sissippi Valley. The report is printed in 

 large quarto form, and the present part is 

 illustrated with about forty plates, besides 

 figures in the text. 



Prof. N. Story-Maskelyne describes his 

 Crystallography as a treatise on the mor- 

 phology of crystals (London: Frowde, 12*. 

 6d. ; New York : Macmillan, $3.50). In ad- 

 dition to giving full descriptions of the sev- 

 eral systems of crystallization, he discusses 

 the properties of zones and the varieties of 

 symmetry possible in a crystalloid system of 

 planes. He also describes modes of repre- 

 senting crystals and of measuring and calcu- 

 lating angles. While the author has deemed 

 it necessary to treat some parts of his subject 

 hi the simplest form compatible with strict 

 geometrical methods, he hopes that his book 

 will not be found lacking in demonstrations 

 that will satisfy students with high mathe- 

 matical training. 



In an easily readable little book Uriel If. 

 Crocker essays to point out The Cause of 

 Hard Times (Little, Brown & Co., 50 cents). 

 He ascribes the recent business depression 

 and that of 1873-'76 to overproduction, and 

 in supporting this view he comes into con- 

 flict with Mill and other authorities of the 

 past and present. One reason that he gives 

 why production outruns demand is that 

 owners of factories frequently prefer to sus- 

 tain a loss that may not continue so long as 

 to be serious rather than the certainly large 

 loss involved in shutting down their works. 



The Brush Arc Light Dynamo, by H. C. 

 Reagan, Jr., is a handbook for electrical en- 



