FOR THE USB OF TEACHERS. 



No. 19. 



Leaflet 



On Nature Study. 



Especially Adapted to the Use of Children in Schools 

 IN Rural Districts. 



PREPARED BY THE 



FACULTY OF PURDUE UNIVERSITY. 



HEAT AND WHAT IT DOES. 



In Ten Short Lessons. 



By Prof. A. W. Duff. 

 I. 



How do you know there is such a thing as heat? You have never 

 seen it, and yet you probably believe there is such a thing. Put a piece 

 of iron out in the sun on a hot day, and after some time feel it. No 

 doubt you will say that it feels hot and that it got its heat from the 

 sun. Now, hold your right hand on the iron for a while and then put 

 your right hand on your left and you will find that your right hand 

 feels hot to your left. Your right hand must have gotten its heat 

 from the iron. This shows that when the iron feels hot it must be 

 giving heat to the hand. Such is always the case; a body feels hot 

 when it is giving heat to the hand. But your right hand felt hot to 

 the left, and, therefore, your right hand must have been giving heat 

 to the left. Now, how did your' left hand feel to the right? You 

 will say that it felt cold. And so you see that when a thing .feels cold 

 to the hand, heat is going from the hand to that thing. So the terms 

 . hot and cold simply refer to the direction in which heat is going. 



Feel the iron of a hammer which has been in a cool place, and then 

 feel the wooden handle. Which seems cooler? Evidently the iron 

 does. Do you really believe that it is any cooler? It is difficult to see 

 how it can be, since both were in the same place. Perhaps it is because 



