The Microscope. 13 



vised (with skilled aid) ever /other chapter in the book, doubled 

 the number of wood-cuts and put in nearly a score of new, 

 colored plates." The latter are excellent lithographs, while the 

 phototypes are nowhere else at the command of the reader 

 unless he have access to the best of foreign microscopical litera- 

 ture. Here will be fou .d a full-page phototype b}- Van Heurck 

 of his best work with the new Zeiss objective of 1.63 N. A.; a 

 full-page photot3qDe of Zeiss's famous resolution of Pleurosigma 

 magnified 4900 diameters; superb illustrations of the secondary 

 structure of diatoms, with much more that is commendable and 

 exceedingly welcome, while man}^ of the optical diagrams are 

 printed in two colors, so that the subject matter is made as 

 simple, as plain, as eas}^ of comprehension as a master-work- 

 man can make it. The reader has to exert but little effort on 

 his own part to comprehend and, it is to be hoped, to appreciate 

 this wonderful display of the latest and the best of things 

 microscopical. That he will appreciate the editor's skill in 

 so simplifying the abstruse should be a foregone conclusion. 

 In reference to this Dr. Dallinger says: "In the following 

 pages we propose to treat the elementarj^ principles of the 

 optics of the microscope in a practical manner, not merely lay- 

 ing down dogmatic statements, but endeavoring to show the 

 student how to demonstrate and comprehend the application of 

 each general principle. But in doing this we are bound to 

 remember a large section of the readers who will employ this 

 treatise, and so to treat the subject that all the examples given 

 or that may be subsequently required by the ordinal* v micro- 

 scopist, maj^ be worked out with no heavier demand upon 

 mathematics than the employment of vulgar fractions and deci- 

 mals." Therefore, the intelligent amateur, or even the intelli- 

 gent novice, need have little fear of the book as of something 

 ponderous and consequentl}'' repulsive. It is learned, it is 

 simple as a natural result, and the microscopists that master it 

 will be well-informed indeed. And every student can master it. 

 For the amateur. Dr. Dallinger has " a fellow feeling."' With- 

 out the amateur there never could have been the microscope of 

 the present day. Without the amateur our objectives would 

 have, perhaps, remained as they were in the days of French 

 Triplets. Without the amateur to start the ball rolling there 

 could never have been the professional to keep up the move- 



