| OCR Text |
Show FIRST TEST OF BAROMETER store Putting Full Reliance on Instrument, In-strument, Certain Procsutlons Are Imperative. - Don't expect a barometer to tell you the truth about the weather until you bave tested It thoroughly. Two common causes for unreliability are air and water mixed with tbe mercury mer-cury In the tube. These can be expelled ex-pelled by boiling the mercury. In order or-der to test a barometer let It hang for a time In the proper position, then gently and v.lth rate incline it so that the mercury nny ctrlke against the glsss tube- If there Is no air within you will hear a sharp metallic click, but if tbe sound Is dull and muffled It Indicates the presence of both air and moisture. Tho presence of air alone Is shown by minute bubbles. If at any time the mercury seems to adhere to the tube even In the slightest slight-est degree, and the convex surfsce assumes as-sumes a more flattened form, it Is safe to conclude that either air or moisture Is present In any of these esses the Instrument should be put Into expert hands for rectification. There are seversl kinds of barometers. barome-ters. The ordinary "weather glass" In common ue Is more or less unreliable unre-liable and is earily made more so by careless hsndllng. In fact, any barometer bar-ometer must be trested with great respect In order to retain Its usefulnessHarper's useful-nessHarper's Weekly. |
