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EXPERIMENTS AND INVESTIGATIONS 



DESCRIPTION OF THE INSTRUMENTS. 

 PLATE XII. 



Is the instrument with two plates or edges. A, B, hori- 

 zontal, D, C, vertical ; the former moved by the screw E, 

 which has also a micrometer for the distances on the scale G ; 

 the latter, in like manner, moved by F, connected with micro- 

 meter and scale H. 



