THE TRAVERSING SUBSTAGE ILLUMINATOR. 69 



useful for obtaining very oblique rays of light with the 

 help of the condenser. This has been accomplished in 

 another way by Messrs. Swift and Son, in their radial 

 traversing substage illuminator. While regretting that 

 this firm could not have found a shorter title for this acces- 

 sory, we must say it seems more generally applicable than 

 most other modes of producing obliquity of light. It is 

 shown in Fig. 47. 



FIG. 47. 



This apparatus has been constructed for the purpose of 

 increasing the resolving property of high-power objectives 

 by causing still more oblique pencils to impinge upon the 

 object than can be obtained by- most methods. The 

 arrangement consists first of an arc-piece, fixed below the 

 stage, radial to an imaginary line drawn through the axis 

 of the microscope objective, in the same plane with the 

 object. On this an achromatic condenser of special con- 

 struction is made to travel, thus keeping the rays of light 

 on the object during its entire traversing. These rays con- 

 verge and terminate in a focus through the front lens, in a 

 highly concentrated form. The condenser is illuminated 



