International Correspondence Schools · Scranton, Pa. : The Colliery engineer co. · leaf 419
PNEUMATICS. 407 watch up to an 8 or 10 inch face. They consist of a cylin-drical box of metal, with a top of thin, elastic, corrugatedmetal. The air is removed from the box. When the atmos-pheric pressure increases, the top is pressed inwards, andwhen it is diminished, the top is pressed outwards… … Fig. 191.cause it to move either to the right or left over a graduatedscale. These barometers are self-correcting (compensated)for variations in temperature. They are very portable,occupying but a small space, and are so delicate that theyare said to show a difference in the atmospheric…
Railroad engineering
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