96 



THE MICROSCOPE 



The limb. 



The 



mechanical 



stage. 



The body. 



a brass stage, as it is less subject to warpiag, is not easily clipped 

 or broken. The stage has four holes for the accommodation of 

 stage clips. The limb is drilled with a hole by means of which 

 a mechanical stage can be attached, held in position by a strong 

 bolt with clamping milled head. This mechanical stage can be 

 fitted by the user of the microscope without returning the 

 instrument to the maker, although it is best to do so if possible, 

 as in this case a steady pin is also put in to ensure that the mechani- 

 cal stage is in its exact position, and thus to make certain that 

 the finder divisions read correctly. The finder divisions read from 

 the left-hand side and the bottom of the 3x1 slip. The standard 

 body of the microscope is of rather larger diameter than is usual 

 Phe with the ordinary small body tube. The coarse adjustment is 



djuatmeuts. actuated by the upper milled head, and the fine adjustment by the 

 lower. The fine adjustment is of rigid type and gives a very 

 sensitive and smooth motion. It has two speeds, the left-hand 

 milled head travelling the body at half the speed of the right- 

 hand milled head. The substages are all interchangeable, and 

 all the microscopes are supplied with the holes necessary for the 

 fitting of any of the various forms of substage which canbe attached 

 by the user with the aid of a screw-driver. Thus a microscope with 

 a plain tubular substage may first be bought, and if the micro- 

 scopist at a later date feels the need of a substage with focussing 

 and centring adjustments, this substage may be purchased 

 separately, and he is able to fix it himself, without sending the 

 microscope to the maker. The following are the dimensions of 

 these microscopes : 



The 



Bubstage, 



Dimensions 

 of the 

 microscope. 



No. 3210. 



6i X 4 X 1 



4f 



m 



7 

 S 



•01 nun. 



•8 in. 



Size of base ...... 



Distance of upper surface of stage from table 



The height of the microscope in use when vertical . 



The height of its optical centre when horizontal 



Diameter of coarse adjustment milled heads . 



Diameter of fine adjustment milled heads 



Travel of coarse adjustment .... 



Each division of the fine adjustment moves the body 

 Travel of fine adjustment ..... 



Diameter of object glass screw. Royal Microscopical 

 ■ Society's Standard ...... 



Diameter of drawtube, Royal Microscopical Society' 



Standard No. 1 

 Diameter of substage, Royal Microscopical Society'i 



Standard ..... 

 Diameter of mirror ...■., 

 Focal length of mirror ... 



Vertical travel of mirror 



Tube length 140 to 



Outside diameter of upper portion of drawtube 



Diameter of object glass stem 



Distance from optic axis to inside of limb 



No. 3210, page 97, is the simplest form of the microscope, 

 and has a plain tubular substage into which slides a fitting with 



•917 



