Microscopes of Powell, Boss, and Smith. By E. M. Nelson. 433 



remained much the same a3 it was before. The following alterations 

 may be enumerated : — 1st, a rectangular bar was substituted for the 

 triangular bar in fig. 114, and the back-stay to the body was omitted ; 

 2nd, the pinions controlling the rectangular stage movements were 



Fig. 116. 



placed parallel instead of at right angles to one another ; 3rd, con- 

 centric rotation was added to the stage ; 4th, a complete substage 

 with'rectangular and rotary movements was supplied. 



It is highly probable that this model was prepared for the Exhi- 



