314 APPENDIX. 



we feel it cold : but, on the contrary, if we have 

 lived in an atmosphere of between. + 40" and -}- 

 5O, if the Heat rise to -f- 6() u we feel it very hot. 

 Again, let two basons of water be taken, one 

 heated only to -f- 35. the other to -f- no, and 

 put one hand into the one, the other into the 

 other bason, for some time: if we then immerse 

 both hands in water 'heated to + 60 Q } we shall 

 with one hand feel this Cold, with the other Hot. 

 Hence it may be reasonably inferred, that we can- 

 not judge with precision of Heat or Cold by the 

 Sensations they excite in us. 



In the next place, we are to consider Heat and 

 Cold as the cause of powers which bodies possess 

 of exciting particular sensations. As to Cold, it 

 Is seldom supposed to be either matter itself or a 

 quality: it is more commonly looked upon as a 

 deprivation of Heat ; for the less the heat, found 

 in a body, the greater the Cold, and vice versa. 

 There are particular cases in which Cold may be 

 produced. i. When some particular chemical 

 attraction takes place, Cold is produced. 2. The 

 conversion of solids into liquids, and of liquids into 

 vapour, produces Cold, as is shewn by chemists. 

 And 3. Cold may be produced by animal powers. 

 It is not intended to relate experiments by which 

 these may be proved : but the grand question 

 which we most wish to determine, is, with respect 

 to Heat, whether it be matter under some parti- 

 cular form, or only a quality. That our reason- 

 ings on this important subject may have the better 

 *ffect, we must first reflect upon the various means 



of 



