Fig. 33 represents the latest improved mechanism of an aneroid. The outer case and the face of the instrument are removed, but the hand is attached by its collet to the arbour. _A_ is the corrugated box, which has been exhausted of air through the tube, _J_, and hermetically sealed by soldering. _B_ is a powerful curved spring, resting in gudgeons fixed on the frame-plate, and attached to a socket behind, _F_, in the top of the box. A lever, _C_, joined to the stout edge of the spring, is connected, by the bent lever at _D_, with the chain, _E_, the other end of which is coiled round, and fastened to the arbour, _F_. As the box, _A_, is compressed by the weight of the atmosphere increasing, the spring, _B_, is tightened, the lever, _C_, depressed, and the chain, _E_, uncoiled from _F_, which is thereby turned so that the hand, _H_, moves to the right. In the mean while the spiral spring, _G_, coiled round _F_, and fixed at one extremity to the frame-work and by the other to _F_, is compressed. When, therefore, the pressure decreases, _A_ and _B_ relax, by virtue of their elasticity; _E_ slackens, _G_ unwinds, turning _F_, which carries _H_ to the left. Near _J_ is shown an iron pillar, cast as part of the stock of the spring, _B_. A screw works in this pillar through the bottom of the plate, by means of which the spring, _B_, may be so adjusted to the box, _A_, as to set the hand, _H_, to read on the scale according to the indications of a mercurial barometer. The lever, _C_, is composed of brass and steel, soldered together, and adjusted by repeated trials to correct for the effects of temperature. A thermometer is sometimes attached to the aneroid, as it is convenient for indicating the temperature of the air. As regards the instrument itself, no correction for temperature can be applied with certainty. It should be set to read with the mercurial barometer at 32 deg. F. Then the readings from it are supposed to require no correction.