380 The Microscope. 



that would otherwise make a circle under the lens appear as an 

 ellipse when drawn on the paper, is simple and must be effect- 

 ive. The micro-spectroscope is also noted, and concise direc- 

 tions are given for its use, with several experiments. This is 

 acceptable, as the instrument is not well understood by the 

 rank and file of working microscopists, yet the apparatus is 

 coming more and more into demand, and may soon be one of 

 the most important of microscopical accessories. The chapter 

 on the polariscope contains much matter not so readily access- 

 ible elsewhere, without much reading and the turning over of 

 many books. The author is to be commended for his invariable 

 use of the word " ocular," for the common term " eye-piece." It 

 would be a benefit to all concerned if the word could be accepted 

 by all writers and speakers on the subject, to the entire exclu- 

 sion of the popular " eye-piece." Yet it seems somewhat of a 

 blemish on an otherwise praiseworthy production, to find the 

 author speaking of high and low oculars, invariably omitting to 

 supply the indispensable word power after each. This is mis- 

 leading and confusing, especially to beginners, be they pupils in 

 Cornell University or beginners with themselves for instructors. 

 Without some explanation, which is not given, the expressions 

 high and low might be supposed to apply to the physical appear- 

 ance of the oculars, which are high and low in height as well as 

 in power, the high being low in power, and the low in height 

 being high in power. Prof. Gage shows the same tendency in 

 referring to objectives, often calling them high and low, with no 

 additional word. With a living teacher to explain, these may 

 not be so misleading as they certainly must be to the ignorant 

 reader, with, no help but this book. It would be much better 

 and quite as easy to refer to oculars by the name of their equiva- 

 lent focus. For " high " and " low " objectives there is absolutely 

 no excuse. Twice on page 3, Prof. Gage refers to the objective 

 as " microscopic," and to " microscopic " apparatus ; on page 

 8 he calls the ocular "microscopic." Objectives, oculars and 

 other microscopical apparatus vary greatly in size, it is true, but 

 they are never microscopic ; and lucky it is for those that use 

 and handle them that they are not. The second page of the 

 cover contains tables of metric and English measures of length, 

 volume and weight, with rules for the changing of the Centi- 

 grade scale to that of Fahrenheit, all of which is acceptable. 



