May 2, 1902.] 



SCIENCE. 



707 



Bennet, F. J. Bell and others, with the re- 

 sult that the volume will remain, as it has 

 been, the most useful and extensive work of 

 reference in this field. The illustrations, 

 always numerous in former editions, have 

 been largely increased and are excellently 

 chosen. 



Especial mention should be made of the 

 chapter of 150 pages on the history and de- 

 velopment of the microscope, the scientific 

 presentation of which is full of interest; with 

 its extensive illustrations, many of which are 

 new, it forms by all odds the most complete 

 study on the evolution of the present form 

 of the instrument accessible to the student. 

 Here is proposed the following scheme for the 

 classification of instruments which makes 

 their criticism and comparison more intel- 

 ligible and constitutes the first effort in this 

 direction. This classification is as follows : 

 Microscopes placed in Class I. possess — 



1. Coarse and fine adjustments. 



2. Concentric rotation of the stage. 



3. Mechanical stage. 



4. Mechanical substage. 

 Class II. 



1. Coarse and fine adjustments. 



2. Mechanical stage. 



3. Mechanical substage. 

 Class III. 



1. Coarse and fine adjustments. 



2. Plain stage. 



3. Mechanical substage. 

 Class IV. 



1. Coarse and fine adjustments. 



2. Plain stage. 



3. Substage fitting (no substage). 

 Class V. 



1. Single adjustment (coarse or fine). 



2. Plain stage. 



3. With or without substage fitting (no sub- 

 stage). 



This classification applies also to portable 

 miscroscopes. 



Of American instruments Dr. Dallinger 

 speaks very highly more than once, saying in 

 one place, 'The recent microscopes of the best 

 American makers are chara,cterized by the 

 highest quality of workmanship and abundant 

 ingenuity,' and especially commending as an 

 'admirable feature' that the makers here 

 "avoid sharp angles and knife-like edges on 



all their instruments. This looks a trifle, 

 but the use of the microscope with saprophyt- 

 ic, pathogenic or other infective material re- 

 quires the utmost caution that the skin of the 

 hands should be unbroken." 



Dr. Dallinger's views on the continental 

 model of stand are so well known that one 

 can not be surprised at the position taken in 

 this work; but the manner in which this opin- 

 ion is expressed is so catholic and the criti- 

 cism is so full of truth that the reader, what- 

 ever his views, feels himself brought into 

 sympathy with the author. The following ex- 

 cerpt shows the tenor of this discussion: 



Our one purpose in this treatise is to promote 

 what we believe to be the highest interests of the 

 microscope as a mechanical and optical instru- 

 ment, as well as to further its application to the 

 ever-widening area of physical investigation to 

 which, in research, it may be directed. To this 

 end throughout the volume and especially on the 

 subject of the value and efficiency of appa- 

 ratus and instruments, we have not hesitated 

 to state definitely our judgment, and, where 

 needed, the basis on which it rests. Inci- 

 dentally we have expressed more than once 

 our disapproval, and, with ourselves, that of 

 many of the leading English and American micro- 

 scopists, of the form of microscope known as the 

 Continental model; we believe it is not needful to 

 say that we have done this after many years of 

 careful thought and varied practice and experi- 

 ence, and, so far as the human mind can analyze, 

 without bias. It is not where a microscope is 

 made that the scientific microscopist inquires 

 first, but where it is made most perfectly. 

 * * * The more recent instruments of Con- 

 tinental model are marvels of ingenuity. • * • 

 There is no fault in the workmanship; it is the 

 best possible. The design alone is faulty; there is 

 nothing to command commendation in any part 

 of the model. * * * To all who study carefully 

 the history of the microscope and have used for 

 many years every principal form, it will, we 

 believe, be manifest that the present stand of the 

 best makers is an overburdened instrument. Its 

 multiplex modern appliances were never meant to 

 be carried by it. 



The chapters on the microscopic forms of life 

 are extensive and well illustrated, yet they 

 constitute the least satisfactory portion of the 

 work; indeed some of the sections are seri- 

 ously out of date. It is the lower types the 



