1851.] The adaptation of the Aneroid for surveying in India. 325 



the atmospheric impressions ; it is corrugated in concentric circles, 

 which increases its elasticity, and renders it more susceptible of atmo- 

 spheric impressions ; b is the tube, hermetically sealed, through which 

 the air in a is exhausted. At the centre of a there is a solid cylindri- 

 cal projection x, to the top of which the chief lever c d e is attached 

 ■ — this lever, which is of the second order, rests upon 2 fixed pins, or 

 fulcra, placed vertically, and upon a spiral spring under d, but it is 

 perfectly mobile. The extremity e of this lever is attached by a ver- 

 tical rod and bow-shaped spring/, with another lever to which a watch- 

 chain g is fastened and extended to h, where it works upon a drum 

 fixed to the axis of the index -hand, connected with a delicate spring at 

 h, — the vertical motion is thus changed to a horizontal one, and the 

 hand, which is attached to the metallic plate i, is thereby moved upon 

 the dial. The movement originating in the vacuum-chamber is multi- 

 plied by these levers, so that a change in the corrugated surfaces, 

 amounting to 1 -220th of an inch, carries the point of the index-hand 

 through a space of three inches on the dial. 



" In Fig. 3. the vacuum-chamber is represented by D ; the large 

 lever by C, resting upon the fulcra B B and spiral spring S, and sup- 

 porting the box D by the pin K. At the extremity of C is seen the 

 vertical rod (I) connecting it with the levers (2 and 3) by the bow- 



shaped spring (4). The square-headed screws b e, by screwing or 



2 u 2 



