Chap. 2.] Firejuljeft to the Laws of Attraction. 1 01 



tact with a cold one, the former lofes a part of its 

 heat, and both of them become equally warm. If 

 heated iron is laid upon a (lone, its heat will 'flow into 

 the (lone ; if thrown into water, the hear will be dif- 

 fufed through the water. If a number of different 

 fubftances, as metals, wood, wool, &c. are brought 

 together into a place v/here there is not a fire, if they 

 are of different temperatures, that is, of different de- 

 grees of heat, the fire will be attracted from the hot- 

 teft to thofe that are colder, till a perfect equilibrium 

 is produced, or till they have all acquired the fame 

 temperature, as may be proved by applying the ther- 

 mometer fucceffively to each of them. 



It does not appear, however, that all bodies have 

 an equal attraction for the matter of fire. If a rod of 

 iron is put into the fire for a more time, the end which 

 is at a moderate dii'tance from the fire will almoft 

 burn the hand ; but a rod of wood, of the fame length 

 will be confumed to afh.es at the end which is in the 

 fire before the other end is fufficiently heated to burn 

 the hand. A ball of lead and a ball of wool may be 

 of exactly the fame temperature by the thermometer, 

 but they will not appear of the fame degree of heat 

 on applying the hand. If they are of a temperature 

 below that of our bodies, the lead will appear much 

 colder than tije wool, becaufe it attracts the heat more 

 rapidly from the hand; if they are of a higher tem- 

 perature, the lead will appear much hotter, from the 

 facility with which it parts with its heat. This pro- 

 perty in bodies is called their conducing power ; and 

 thofe bodies through which the element of fire moil 

 rapidly circulates, are called good conductors. 



The power of conducting the matter of fire feems 



*o depend upon the texture of bodies, that is, upon the 



H 3 contact 



