Miscellaneous Intelligence. 



289 



i. 



therefore, constructed an instrument, somewhat in shape of a common 

 watch. It consisted of a bowl of strong iron, or copper, upon which 

 was a domed cover of very thin sheet steel, the edges fitting with great 

 exactness. Springs fixed in the bowl keep the cover at a proper ele- 

 vation ; the air is pumped 

 out, and as the resistance of 

 the springs is uniformly the 

 same, the cover plate rises, 

 or falls, as the atmospheric 

 pressure varies, and these va- 

 riations are shown by means 

 of a hand, securely fastened, 

 passing backward and for- 

 ward on a divided plate. M. 

 Conte, however, was compel- 

 led to reject the instrument, 

 on account of the prejudicial 

 influence which change of 

 temperature had upon it. It 



was left to Mr. Vidi's ingenuity to construct an instrument on scientific 

 principles, in which he "has been most completely successful, and in 

 which he has adopted most ingenious means for correcting the varia- 

 tions of temperature — viz. : by the introduction of gas into the vacuum 

 vase of the instrument ; and, on its capacity being diminished by heat, 



the gas contained within it is, by the same cause, expanded, and resist- 

 ing the compressing force of the atmospheric weight upon the dia- 

 phragms, keeps them separated at a due distance, and effects the com- 

 pensation. The Aneroid barometer consists of a vessel of the shape 

 and size of a chronometer — the inter- 

 nal arrangement of which is shown by 



2. 



h 



D, D, is the vacuum vase ; C, 



C, a lever, resting on its fulcrum B 



B, and spiral spring S — to the end of 

 which is attached a vertical rod, 1, 

 which serves to connect the lever C 



C, with the levers 2 and 3. These are 

 connected by a bow piece, 4 ; and two 

 square-headed screws, at e, b, admit, by 

 screwing or unscrewing them, such an 

 alteration of the distance of leverage, 

 as to allow the hand of the Aneroid to 

 move over a space corresponding with 

 l "e scale of a standard mercurial ba- 

 rometer ; to the end of lever, 3, is at- 

 tached a light rod, terminating with a 



P»ec e of watch chain, attached to a small . 



rol 'er. On the axis of this roller, the hand is fixed, and kept in its po- 

 sition, by means of a spiral spring— the outer coil of which is seen at- 

 tached to the axis. M is the socket, which, being pulled by the pin, k, 

 P'aces the vase in a state of tension, whereby it offers resistance to the 

 Pressure of the external atmosphere ; and the diaphragms are kept 



Second Series, Vol. VIII, No. 23.— Sept., 1849. 3? 



