HEAT. 145 



Some species of fevers indeed have cold and shi- 

 vering fits ; but these are occasioned by the mo- 

 tion, as it were shrinking back from the resist- 

 ance, and the pulse languishes during them, just as 

 it does in fainting. The fire of life smoulders, as it 

 were, at those times ; and if they continue too 

 long the resistance is consolidated and the system 

 will not re-act, but the patient " goes off in a fit.'* 

 That part of the subject is, however, very nice ; 

 and it requires to be treated with a little more of 

 general philosophy than has yet been bestowed 

 upon it, notwithstanding the number of able and 

 eminent men by whom it has been treated. 



Whether it is in the living body or in any other 

 kind of matter, in any state where there is no 

 resistance to motion there is no production (as we 

 call it) of heat ; that is, there is no heat which 

 becomes sensible either to the touch of the human 

 hand or to any other test. Different kinds of 

 matter resist differently, according to the nature 

 of the cohesions by which they are held together. 

 Thus, some of the compound metals melt in the 

 palm of a healthy person's hand, while platinum is 

 stubborn in even the hottest common furnace. 

 Some too, such as arsenic, pass into vapour the 

 instant that they are melted ; while others, such 

 as gold, melt at a temperature not very high, but 

 if pure can hardly be changed into vapour by any 

 ordinary heat. 



The cohesion of matter resists the motion of 

 its particles from each other, which is the effect 

 that the heat in all cases tends to produce, and 

 which if urged far enough it in every case 

 actually does produce. As there is no power of 

 mere adhesion between mass and mass, mechani- 



