210 THE HISTORY AND DEVELOPMENT OF THE MICROSCOPE 



ami eye-pieces that give it magnifying powers ranging from 15 to 

 1,500 times. This instrument is shown in fig. 169, and with the two 

 stands immediately preceding it furnishes us with a fair view of 

 the principal and latest types of the Continental microscope fitted 

 with the apparatus essential to the production of good work. 



But another most interesting model of Reichert's has just been 

 finished which, from its size and approximation to the English 

 stand in some important points, we are constrained to notice as 

 these sheets are passing through the press. The instrument is 

 illustrated in fig. 169 A. The height of the stand in the position 

 illustrated is 16^ in. The distance between the foot and the stage is 

 3 J in. The sub-stage is provided with centring screws, and is raised 

 and lowered by rack and pinion. The mirror can be readily moved 

 towards or away from the sub-stage or can be entirely removed. 

 The tube length with both tubes (A A') extended, including the nose- 

 piece, is 10^ in. The stage is mechanical, and the circle is divided into 

 360 degrees ; both the horizontal and vertical motions of the stage have 

 scales read by verniers. The object is fixed on the stage by spring 

 fittings. The fine adjustment has two speeds of motion by two screws, 

 the one 0'3 mm., the other O'l mm. per revolution, shown at M M7. 

 The draw-tube has a divided scale and is moved by rack and pinion. 



We may now with advantage consider the different classes of 

 microscopes manufactured by the opticians of Europe and America. 

 To do this without prejudice and with efficiency it is necessary to 

 designate the characters which should distinguish each class. 



Microscopes placed in Class I. possess 



1. Coarse and fine adjustments. 



2. Concentric rotation of the stage 



3. Mechanical stage. 



4. Mechanical sub-stage. 

 Class II. 



1. Coarse and fine adjustments. 



2. Mechanical stage. 



3. Mechanical sub-stage. 

 Class III. 



1. Coarse and fine adjustments. 



2. Plain stage. 



3. Mechanical sub-stage. 

 Class IV. 



1. Coarse and fine adjustments. 



2. Plain stage. 



3. Sub-stage fitting (no sub -stage). 

 Class V. 



1. Single adjustment (coarse or fine). 



2. Plain stage. 



3. With or without sub -stage fitting (no sub-stage). 

 This classification applies also to portable microscopes. 



The recent microscopes of the best American makers are 

 characterised by the highest quality of workmanship and abundant 

 ingenuity, but the Continental model is confessedly made their fotmda- 



