254 THE HISTORY AND DE\ 7 ELOPMENT OF THE MICROSCOPE 



milled heads, A. The arm, which is focussed by an excellent spiral 

 rack- work adjustment, carries either a Zeiss dissecting microscope, 

 which, with and without its concave eye-lens, yields six different 

 powers, varying from 15 to 100 diameters, or the arm will receive 

 the very fine Zeiss- Steinheil simple magnifiers. 



The instrument is provided with a large plane and concave 

 mirror on a jointed arm. The utility of this simple microscope is 

 very great, and we do not hesitate to pronounce it the best thing of 

 its class we have ever seen. 



The Continental Model, Our one purpose in this treatise is to 

 endeavour to promote what we believe to be the highest interests of 

 the microscope as a mechanical and optical instrument, 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 apparatus and instruments, we have not hesitated 

 to state definitely our judgment, and, where needed, the basis on 

 which it rests. Incidentally we have expressed perhaps more than 

 once our disapproval, and, with ourselves, that of many of the leading 

 English and American microscopists, of the form of microscope known 

 as the Contiiwntal model ; we believe it is not needful to say that we 

 have done this after many years of careful thought and varied 

 practice and experience, and, so far as the human mind can analyse, 

 without bias. It is not where a microscope is made that the 

 scientific microscopist inquires first, but where it is made most 

 perfectly, and we cherish strong hopes, in the interests of the science 

 of microscopy, that so enterprising and eminent a firm as that of 

 Zeiss, of Jena, will bring out a model that will comport more com- 

 pletely with the needs of modern microscopical research than even 

 the best of the models that they now produce. It is to this house, 

 under the cultivated guidance of Dr. Abbe and Dr. Czapski, that 

 we are indebted for the splendid perfection to which the optical side 

 of the microscope has been recently brought ; and when we know 

 that the ' Continental model ' has, in the hands of the firm of Zeiss, 

 passed from an instrument without inclination of the body into an 

 instrument that does so incline, and from an instrument without 

 sub-stage or condenser into one provided with the latter of these 

 absolutely indispensable appendages, and finally from an instrument 

 with a perfectly plain stage with ' clips ' into what is now a stage 

 with mechanical movements we can but hope that these concessions 

 to what has belonged to the best English models for over forty years 

 may lead to an entire resoiistruction of the stand a wholly" new 

 model intended to meet all the requirements of modern high-class 

 work in all departments, and with a fine adjustment of the most 

 refined class. We cannot doubt, if this were so, that the same 

 genius which has so nobly elevated the optical requirements of the 

 instrument would act with equal success on its construction and 

 mechanism. We have been told in the friendliest spirit, by one 

 deeply interested in the Continental stand, and a master in optical 

 knowledge, that on the Continent the microscope is ' actually almost 

 exclusively used' in a vertical position. Nevertheless we know 



