162 



the above. Credit is due Mr. ti. P. Hobbs for his assistance in devising 

 the mechanical parts. 



FROG TABLES. 



These tables are modifications of those used in the University of 

 Pennsylvania, and meet certain requirements better. They consist. Figure 

 6, of a brass plate 4i^"x8", to which is glued a single piece of cork y/' 

 thick, and the adjustable arm or support. The adjustable part consists 

 of a brass block (c) which slides upon the square rod (e), the set-screw (b), 

 and has a horizontal play of 4i/^". The set-screw (ai allows of a further 

 circular movement of the plate, and the square supporting arna is held to 

 the staud by a luiiversal clamp. 





