ANIMA 



CHAPTER III. 



Latent and sensible Heat. Heat applied to Ice forms Water, and 

 to Water, makes Steam. 



414. THE warm-blooded animals breathe more than the 

 cold-blooded, The same difference prevails among the sub- 

 divisions of these classes, for the warmest kinds breathe more 

 than the coldest. It would seem, then, that the internal heat 

 arises out of, or is in some way connected with, respiration. 

 And this we find to be strictly true, upon examination of the 

 nature and properties of the elements of air, and of the 

 chemical effects produced by this gas upon the blood and 

 particles of the animal body. 



415. When ice is melted and changed to water, it is easy 

 to see that heat is given to it, and absorbed by it. The heat 

 necessary to produce this change has united with the ice, 

 and both together have become water. Again, if much more 

 heat is applied to this water, it boils and is changed to vapor 

 or steam. By continuance of the same process that pro- 

 duced the first change, the second one is produced ; and, by 

 the union of heat with water, steam is formed. It is obvious 

 that steam contains more heat than water, and water more 

 heat than ice. Heat added to ice produces water, and heat 

 added to water produces steam ; and, in both cases, most of 

 the heat becomes latent or hidden in the new substance. 

 If, now, we reverse the process, and return the steam back 

 to water, heat must be given out. Just so much is given out 

 as was originally required to convert the water into steam. 

 If we continue this process further, and change the water to 

 ice, there must be a further discharge of heat; and as much 

 heat will be given out, in this process of freezing the water, 

 as was before required to melt the ice. 



416. There is a general law of matter, that rare or light 

 substances require more heat than dense or heavy matters. 

 Liquids commonly require more heat than solids, and gases 

 more than liquids, to keep them in their respective states; 



