The Limb 27 



There is also another form, now almost non-existent, 

 which is fitted to the microscope at the nosepiece end, and 

 consists of a milled head attached to the body, by means of 

 which a tube which carries the objective is raised and lowered 

 inside the body-tube against a spring. This can never work 

 thoroughly well, for if two round tubes are perfectly fitted 

 one inside the other, they clutch, and to overcome this, one 

 of the tubes has to be rendered a little eccentric, and con- 

 sequently a lateral shake arises. 



In the choice of a fine adjustment, therefore, reject the 

 direct acting and the nosepiece forms. 



THE LIMB. 



The design of the limb of the microscope is of special 

 importance, because it carries the body and is intimately 

 associated with the fine adjustment. It should be of a 

 substantial shape and strongly made. In our opinion the 

 pattern which is shown in the build of microscopes, pages 

 8, 25, etc., is to be preferred before that shown on page 12, 

 because in the former, additional solidity is imparted to the 

 body fittings on account of there being no separate adjust- 

 ment which has to act and re-act at the back part — in other 

 words, a limb which carries the body at one extremity, and 

 at the other is acted upon by the fine adjustment through 

 a pillar, cannot in the nature of things be so satisfactory 

 as a limb which carries the fine adjustment instead of being 

 supported by it. Still, it cannot be denied that the method 

 of attaching the limb to the pillar adopted by the majority 

 of the Continental makers, and, for the matter of that, 

 those English manufacturers who include this style of 

 instrument amongst their models, is usually a very sub- 

 stantial one. 



THE BODY-TUBE. 



It has always been the custom, in the construction of the 

 full-sized English microscopes, to make the body of fairly 

 large diameter ; while on the Continent the reverse is the 



