IMPROVED THERMOMETER. 249 



placed horizontally, though the ivory will be equally pufhed 

 forwards by the mercury, while this is expanded by an increafe 

 of temperature, yet mould the mercury again contract, the 

 ivory will not follow it, but remain ftationary, and confe- 

 quently the point at which it refts will mark the higheft degree 

 to which the thermometer had rifen. An inftrument of this 

 kind is rectified by bringing the ftem into a vertical fituation 

 with the bulb undermoft, then cautioufly reftoring it to a hori- 

 zontal fituation. 



Two thermometers fuch as thofe above defcribed, one filled 

 with fpirit of wine, and the other with mercury, may conve- 

 niently be difpofed upon one frame. If their bulbs be fituated 

 at the oppofite ends of the frame, or as reprefented by the fi- 

 gure, then both may be rectified by the fame movement, and 

 we fhall have an opportunity of afcertaining, by the fituation 

 of the conical pieces in the different ftems, both the higheft 

 and the loweft point which the fluids of the thermometers have 

 reached during any interval of our obfervations. 



Vol. III. I i XIIL 



