

HEAT. 149 



and burning in the robust than in the weak. Some 

 species of fevers indeed have cold and shivering fits ; 

 but these are occasioned by the motion, as it were, 

 shrinking back from the resistance, 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 con- 

 solidated and the system will not react, but the pa- 

 tient " 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 resist- 

 ance 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 dif- 

 ferently, 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 tem- 

 perature 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 pro- 

 duce. As thre is no power of mere adhesion be- 

 tween mass and mass, mechanically united, how 

 small and how close soever the masses may be, 

 which can resist the force of crystallization between 

 the ultimate atoms of the same kind of matter; so 

 also there is no power of crystallization that can 

 N2 



