1865.] Tlie Construction and Use of the Achromatic Microscope. 547 



as it may be well supposed, accurately, the various parts of the instru- 

 ment ; gives excellent directions for practising different methods of 

 illumination, by natural and artificial light ; with the aid of the para- 

 bolic condenser and the "Lieberkuhn ;" and describes the various forms, 

 and the modes of employing the polariscope. The Binocular micro- 

 scope, too, is treated at some length, and illustrations are given to 

 exhibit its superiority over the simpler form of the instrument. 

 The auxiliary appliances, such as the camera lucida, live-boxes, com- 

 pressors, micrometers, lamps, dissecting instruments, mounting appa- 

 ratus, &c. &c, are all described, and the whole subject is fully illus- 

 trated, so as to render any misunderstanding impossible. 



As for the illustrations, they are unique. The text occupies 134 

 pages, and the work contains 76 woodcuts and 27 plates, many of them 

 well executed by the author himself, and all of the first order ; some 

 of the delineations of illuminated test-objects and polarized specimens 

 equal in artistic beauty anything of the kind that we have seen. 



Eegarded as a treatise on the microscope and its uses, the work is, 

 however, far from being complete, and we are sorry to perceive that 

 the author has ministered so largely to the popular, and perhaps 

 fascinating taste for diatom hunting. No doubt those organisms, 

 " diatoms " and " desmids," form very suitable test-objects, and 

 display the powers of a microscope to great advantage, but they create 

 rather a love of display on the part of the owners of a good instru- 

 ment than a desire to turn it to practical account, and we confess that 

 we shall welcome the day when the furore for collecting diatoms has 

 passed over. Then, when scores of amateurs have put their instru- 

 ments (we had almost said their "playthings ") on the shelf, medical 

 men, chemists, physiologists, and micro-geologists, will be found to 

 be the true patrons of the instrument, and microscope makers will (as 

 some of them do already) recognize the truth that it is for the pro- 

 gress of science and to ameliorate the condition of the human race, 

 that the use of the instrument has been revealed to man. 



A remarkable omission, too, in the work before us, seems to be 

 the absence of any mention of micro-photography, or of the apparatus 

 employed in the development of this most interesting branch of 

 microscopical science. If this omission is to be explained on the 

 ground that the author's firm does not interest itself in the art, then, of 

 course, it must be reckoned as one of the disadvantages of the work 

 being an adjunct to their own labours only, but surely it would in no 

 way injure them, and would materially increase the value of the book 

 in a literary sense, if some details were added in a later edition con- 

 cerning the application of the camera, and even of the spectroscope, to 

 the instrument so ably described by the author. 



Of the publisher's share in the work it is hardly necessary to 

 speak. Mr. Van Voorst appears to be determined that whilst his name 

 is linked with science, it shall add lustre to its efforts, and it is always 

 with renewed pleasure that we take in hand a fresh volume from his 

 workshop, our sole regret being that they are so few and far between 

 as compared with former times. 



We wish Mr. Beck a large circulation for his interesting work, and 



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