Handy man's workshop and laboratory . has been put in, andthe stem of the glass sphere in-serted so that the end of the tubeis under the surface of the liquid,the air thermometer is scale of degrees marked on card-board may be put back of the tube,or the gradations may be scratchedon the glass itself, but the readingswill be inaccurate, for they willvary with every barometric varia-tion, since the air pressure on theliquid in the bottle fluctuates. Inonly a modified and rather complexform can the air thermometer berelied upon for exact measurement. The delicacy in action of the air
Handy man's workshop and laboratory . has been put in, andthe stem of the glass sphere in-serted so that the end of the tubeis under the surface of the liquid,the air thermometer is scale of degrees marked on card-board may be put back of the tube,or the gradations may be scratchedon the glass itself, but the readingswill be inaccurate, for they willvary with every barometric varia-tion, since the air pressure on theliquid in the bottle fluctuates. Inonly a modified and rather complexform can the air thermometer berelied upon for exact measurement. The delicacy in action of the air thermometer makes it veryuseful in detecting sudden local changes in temperature. Inter-esting experiments can be performed with it; for instance, if apiece of filter paper saturated with ether is placed on the bulb,the eosin quickly rises because of the heat absorbed in evapora-tion. Because of its inconsistencies in readings, however, it iswrongly named as a definite measurer of temperature, for it isreally only a thermoscope.—15. Fig. 171—A home-made airthermometer I9: HANDY MAN S WORKSHOP AND LABORATORY HOW TO MAKE AN ELECTRICAL ANEMOMETER The velocity of the wind is usually measured by noting therate of rotation of a small wheel driven by the wind. In theinstrument described below, the pressure of the wind is used as <?-s
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