MR. GRUBB'S IMPROVEMENTS. 



those forms whereby the same effects may be obtained by 

 other means. In 1854 Mr. Grubb, of Dublin, in a Pro- 

 visional Specification for Improvements in Microscopes, 

 stated, " My third improvement consists in the addition of 

 a graduated sectorial arc to the microscope concentric to 

 the plane of the object in situ, on which either the afore- 

 said prism or other suitable illuminator is made to slide, 

 thereby producing every kind of illumination required for 

 microscopic examination, and also the means of registering 



FIG. 13. 



or applying any definite angle of illumination at pleasure." 

 This seems to be the embryo of the modern swinging sub- 

 stage, which was not, however, developed in this country 

 until Zentmayer, in America, produced stands with these 

 modifications in the regular course of business. 



As an instance of the pattern and the price at which 

 these stands are sold in the United States may be men- 

 tioned the Biological stand sold by Bulloch of Chicago. 

 The microscope stands I2j inches high and the stage 



