HEAT. 



CHAPTER I. 

 TEMPERATURE. 



Introductory Remarks Temperature Thermal Equilibrium Construction of 

 Mercury -Glass Thermometers Fixed Points: Centigrade, Fahrenheit, and 

 Reaumur Scales Marking Fixed Points Calibration and Graduation Pre- 

 cautions in use Limits of accuracy Range Scales of temperature given by 

 expansion arbitrary The Work Scale Air and Hydrogen Scales Platinum 

 Resistance Thermometers Table of Temperatures Maximum and Minimum 

 Thermometer T hermostats. 



Introductory Remarks. In the science of Heat, we investigate those 

 phenomena which are chiefly revealed to us by our sense of warmth or 

 cold. We use the words " hot " or " cold " to describe the condition of 

 external bodies which corresponds to the sensation we receive through 

 our skin on touching or approaching them, and we habitually compare 

 bodies with respect to the sensations so received, describing one as 

 "hotter" or "colder" than another. Given several vessels of water, 

 we could with very little trouble arrange them in order of hotness, and 

 we have a number of expressions in common use to describe their con- 

 ditions, such as "ice-cold," "cool," "chill taken off," "tepid," "luke- 

 warm," "warm," "hot," "boiling hot." Our primary sensations are, 

 therefore, those of hotness or of coldness, and we are accustomed to think 

 of hotness as varying in degree. If we put a hot body in contact with a 

 cold one if, for instance, we pour hot water into a cold vessel the hot 

 water is cooled while the cold vessel is heated. We regard this change 

 as the passage of something which we term heat from the hotter to the 

 colder body, its loss by the former being accompanied by cooling, its gain 

 by the latter by heating. We do not mean to imply by " something " some 

 kind of matter. We may fairly describe kinetic energy as " something," 

 and say that when one body strikes another, setting it in motion, " some- 

 thing," .viz., kinetic energy, has passed from the one to the other, yet 

 we do not think of energy as matter. 



So, here, we only describe the heat as " something," because we 

 believe that we can identify the heat gained by the cold vessel with that 

 lost by the hot water. We also think of heat as greater or less in 

 amount. If the hot water cools very considerably, we think of it as 

 giving up more heat than if it cools only slightly. Or if the quantity of 

 hot water cooling is comparatively large, we think of it as giving up more 

 heat than a smaller quantity of water cooling to the same extent. 



A 



