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Experiments and, Observations on theHEAT and COLD produced by theMECHANICAL CONDENSATIONand RAREFACTION of AIR.

BY JOHN DALTON. >

READ JUNE 27 , 1800 .

If a thermometer be inclosed in a receiver an4the air suddenly condensed, the thermometerrises a few degrees above the temperature of theatmosphere ; apd if the air be exhausted from areceiver inclosing a thermometer, the mercurysinks a few degrees immediately ; but in bothcases after some time it resumes its former sta-tion. These facts are well known to philoso-phers of the present age, but they do not allagree in the explanation of them. Thinking thesubject worthy of elucidation, I was induced toinstitute a series of experiments for the purpose,jyhich I apprehend have led to a clear demon-stration of the cause of the phenomena, andmoreover make the facts themselves appear in asomewhat different point of view from what theyare seen in at the first moment.