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Transactions of the Society. 



the body, but in Adams' " Universal Double " Microscope the 

 screw, at the bottom of the pillar, moves the stage. 



Watkins in this design has therefore reversed the motions of 

 Adams' earlier Microscopes by changing a stage tine into a coarse- 

 adjustment, and a body coarse into a fine-adjustment. 



The principal fault in Watkins' design is that the instrument 

 is too much like a split-cane fishing rod. It is all on springs ; it 

 cannot be touched without its shaking like an aspen. The folding 

 tripod is a spring ; the compass joint on the limb is in a totally 

 wrong position, viz. at the end where it manifestly is devoid of any 



Fig. 28. 



balance ; the difficulty, therefore, of bringing this Microscope, on 

 account of its instability, to a correct focus can be imagined. 

 The arm which holds the body, and which is at right angles to 

 the limb, is a thin plate of silver, far too weak for its work. 

 It is important thus to trace the faults of this old Microscope, 

 for by doing so we are enabled to find out what influence the 

 design had in Microscope construction ; for if we examine the 

 Microscope that next followed it, viz. Adams' " Variable " (fig. 28), 

 we shall see what points in Watkins' design were retained, and 

 what rejected as faulty. We find, then, that the folding tripod, 

 vertical pillar, and the inclinable limb are retained, but the limb 



