14 HISTORY OF THE MICROSCOPE. 



Zentmayer, Sidle, Spencer, and Gnndlacli, prove 

 worthy rivals of those of London makers. Indeed, the 

 Ross-Zentmayer model has been generally admired, 

 and its principle of construction is admittedly of the 

 highest order of mechanical skill. On the Continent, 

 Hartnach, Zeiss, Mertz, Verich, Nacliet, etc., hold 

 equal rank as makers of first-class instruments. 

 Hartnach's accurately fitted concentric stage is the 

 admiration of microscopists, and has consequently 

 "been very generally adopted. The greatest and most 

 important improvement the instrument has received 

 is that of the immersion objective. Amici, some fifty 

 years ago, first applied the immersion system. Pro- 

 fessor Scemmering, writing of its adaptation to a 

 microscope of Amici's, says of it, " Its magnifying 

 power, and the admirable precision and clearness with 

 which the object is s-een, seems astonishing." The 

 immense importance of the system was only slowly 

 realized in England, and when, some ten or a dozen 

 years ago, the Author and Mr. John Mayall, Jun., made 

 an attempt to bring the immersion objective to the 

 notice of the Microscopical Society, much opposition 

 was offered, especially by opticians. Its advantages are 

 now fully acknowledged ; it is understood to give in- 

 crease of light, superior definition and clearness to the 

 optical image, an image obtained by simpler means of 

 illumination, whilst a much greater working distance 

 between the object and the objective is secured. 



Further improvements remain to be noticed ; first, that 

 of the adaptation of the " Homogeneous Immersion " 

 system, the principle of the construction of which is 

 also due to Professor Amici ; its realization for micro- 

 Jjficopy is, however, the work of Messrs. J. "W. Stephen- 

 son, and of the learned Professor E. Abbe, of Jena ; 

 secondly, that effected in the microscope stand itself, 

 as my pages were passing through the press " The 

 Universal Inclining and Rotating Microscope," devised 

 by Mr. Wenham, to whom the instrument is already so 

 much indebted. This great change in the form of the 

 instrument has been made with the special object of 

 obtaining a large range of effects of oblique light both 



