CONTINENTAL V. ENGLISH MODEL 255 



what elaborate arrangements have been made to enable the body to 

 be inclined in all the better models, and surely the English stand is 

 as capable of being used in this position as the most primitive Con- 

 tinental instrument ; but the doubt we have is as to whether the 

 most primitive Continental stand possesses the same primal adapta- 

 bility to all the modern optical and mechanical improvements of 

 the microscope as is possessed by the English stand. It is said 

 that ' the Continental microscope has closely followed the wants of 

 the microscopist, and that in its mechanical arrangements it has kept 

 pace with the increasing improvement of the optical parts, without 

 outrunning them, as has been the case with many English forms of 

 construction.' "With the deference and good feeling with which we 

 receive this statement we are bound to say that it does not present 

 itself as historical. The mechanical parts have not in reality kept pace 

 with the optical improvements, for when apochromatic lenses of 0'95 

 N.A. to 1'4 N.A. are used with large illuminating cones they become 

 so sensitive to focal adjustment that the Continental fine adjustment 

 (the best form of which has hitherto been used by Zeiss) is not 

 sufficiently slow to permit of accurate focussing in highly critical 

 work. Applications have, for instance, been made to Powell, asking 

 him to increase the slowness of his fine adjustment, which is now 

 twice as slow as the best Continental form. But perhaps the 

 clearest evidence is found in the fact that, while we are passing this 

 book through the press, two striking proofs of Continental conviction 

 that their fine adjustment should be rendered slower and more sen- 

 sitive are given, first, by the beautifully simple and, as we believe, 

 most admirable invention of Reichert, adapting a lever movement 

 to his stands (vide p. 169, fig. 131), by which he makes the fine 

 adjustment more than three times as slow as the best hitherto used 

 on the Continent ; while the firm of Zeiss themselves, in their 

 newest model (p. 167, fig. 128), have by another method sur- 

 passed all other makers; and, as I learn by the courtesy of the 

 firm, 'the micrometer screw of this new stand is adjusted for 

 ,.g- 3 -th of an inch for each revolution of the milled head ' (figs. 129, 

 130). 



We cannot but believe that this is the best evidence we can 

 have of the validity of our contention in the last edition of this 

 book that the Continental fine adjustment was too coarse or quick 

 for the almost perfect objectives and eye -pieces they themselves had 

 given to the world. 



We have written throughout this book too frankly of the eminent 

 services of Messrs. Zeiss, to the furtherance of the interests and pro- 

 gression of the microscope as a scientific instrument, to be misunder- 

 stood in making a plain estimate of the quality of the model on which 

 their elaborate and in some senses beautiful stands are built. It 

 will be seen that we everywhere justify our judgments by plain and 

 easily comprehended reasons, and the very eminence of the makers 

 renders it incumbent that practical microscopists should, without a 

 shade of bias, assess the value of a stand which is certainly not 

 built on lines that contribute to a higher and still more efficient, 

 microscopy 



