66 



THE AMERICAN MONTHLY 



[Marchi, 



How TO See with the Micros- 

 cope. — The long-expected book of 

 Prof. J. Edwards Smith, with the 

 above title, has at last been published 

 by Messrs. Duncan Brothers, of 

 Chicago. It is difficult to form an 

 estimate of the value of the book to 

 the general microscopist. As an expo- 

 sition of the author's opinions as to 

 the intrinsic value of various ob- 

 jectives and the usefulness of wide 

 angular apertures it posesses some 

 interest, for his opinions are based 

 upon the results of practical ex- 

 perience in testing them ; but opi- 

 nions of this kind are often misleading, 

 unless they are guided by a regard 

 for underlying principles, and so far 

 as we are able to judge. Prof. Smith's 

 conclusions are purely empirical. 



While we do not doubt that the 

 student would find many useful hints 

 regarding the manipulation of the 

 microscope for the resolution of the 

 most difficult test-objects, and some 

 very practical and excellent hints 

 about stands, and the examination of 

 objectives, we are forced to conclude 

 that further than this the book 

 posesses but little value. 



The discussion of angular aperture 

 is very diffuse, and it is clear that the 

 author is not familiar with the subject 

 in its theoretical relations. No refer- 

 ence is made to numerical aperture, 

 but on page ii8 we read that 

 " ' angular aperture' per se is not a 

 fixed and definite quantity nor one 

 that can be fenced in and subjected 

 to any fixed rules. Nothing definite 

 in the way of rigid law can be applied 

 to it," which is a remarkable assertion 

 to make at this late day. However, 

 it appears that the author has totally 

 ignored any correct methods of 

 measuring angular aperture, but still 

 abides by the old-time custom (p. 96). 



Balsam-angle is touched upon, very 

 lightly however, and a brief allusion 

 is made to oil-immersion objectives, 

 but the learner must seek elsewhere 

 for any useful information upon these 

 subjects. 



The illustrations on page 244 are 



very misleading if they are intended 

 to represent, even diagrammatically, 

 the manner in which oblique light is 

 supposed to reveal striae ; but perhaps 

 we do not fully understand their 

 significance. 



From a scientific point of view, the 

 book is already far behind the times. 



The " Supplement " contains a list 

 of Prof. Smith's contributions to the 

 subject of objectives, and reprints of 

 a series of letters which were written 

 by him in the course of a controversy 

 between the author and the Editor of 

 this Journal. It is to be hoped that 

 these letters will be highly edifying to 

 the readers of the book, but in case 

 any of them should have occasion to 

 refer to the replies to those letters, 

 which are not published in connection 

 with them, we deem it proper to re- 

 mind them that they were written four 

 or five years ago, and although we be- 

 lieve that our opinions have not since 

 undergone any very radical changes, 

 we were not then familiar with the la- 

 bors of Prof. Abbe and others, and per- 

 haps now we would express them in 

 somewhat different form. However, 

 we may feel consoled by the reflection 

 that our name has been inscribed 

 upon the pages of a book that will 

 doubtless find many readers, and that 

 it will thus become known to coming 

 generations, even though not under 

 circumstances most favorable for 

 appreciation and fame. 



The book contains over 400 pages, 

 with illustrations of stands and some 

 accessories. It is printed on good 

 paper, but the typographical work 

 is inferior and the binding is poorly 

 done. 



Sprouting Milk Globules. — A 

 long article, by Henry A. Mott, Jr., 

 Ph. D., etc., has lately been published 

 in The Ajnerican Dairyman, which 

 would afford an excellent text for a 

 discourse about false interpretations 

 of common facts. An illustration, 

 copied from M. Turpin, accompanies 

 the article, and its purport is to show 



