20 



THE MICROSCOPE 



ReTolving 

 nosepiece. 



Sloan object 

 changer. 



has more than once made such a mistake and wondered why he 

 could not focus his specimen. 



The nosepiece (S) of a microscope is the lower end of the 

 body (M) provided with a screw for attaching object glasses. A 



revolving nosepiece is an appliance which 

 screws into the nosepiece and which 

 carries a revolving plate into which two 

 or three object glasses can be fixed, 

 known as double or triple nosepieces 

 respectively. By rotating the revolving 

 plate each object glass can be rapidly 

 Fig. 7. — ^No. 3301, Dust- brought into use, being held in the 

 tight Triple Nosepiece. correct position by a spring clip. The 

 best form is made so that no dust can drop into the back of the 

 object glasses and they can be safely left attached to the micro- 

 scope. The extra length of the body caused by the length of a 

 nosepiece is 15 mm., and the drawtube should be closed by that 

 amount or set at 145 mm. instead of 160 mm. 



An object glass changer is an apparatus for rapidly changing 

 the object glasses by another method. Each object glass is 

 screwed into a fitting which slips into an adapter that is fixed to 

 the nosepiece of the microscope, and as each fitting is provided 

 with two adjustable abutment screws the object glasses can be 

 individually adjusted so that they exactly register as regards 

 the position of the field of view. Changing an object glass by 

 this means is nearly as rapid and more accurate than that of a 

 revolving nosepiece, and is far more convenient when the object 

 glasses are to be used on 

 different instruments or where 

 more than three are used. 



It consists of an adapter 

 which has on one side a 

 sloping projection (A), and 

 on the other a clamp screw 

 (B) which actuates a bevelled 

 nut (C). The adapter is 

 clamped to the nosepiece of 

 the microscope by a screwed 

 ring (D), which is provided 

 with slots, into which a half- 

 penny will fit for tightening 

 it 'up. 



Loose fittings (Fig. 9) are 

 supplied, one of which is screwed on to each object glass. 



Each fitting has a bevelled gap which fits loosely over the 

 bevelled nut (C) of the adapter and swings round into position 

 when a turn of the milled head (B) forces the fitting against the 

 sloping projection (A) and holds it firmly in position. Each 



'•«w..* ^ 



Fig. 8.— No. 3280, Sloan Object 

 Glass Changer. 



