HEAT 8 I 



these larger phenomena, which can be performed in the school 

 room with small trouble, very simple apparatus, and without the 

 requisite of a technical training in physics and chemistry. 



The lessons that follow must necessarily be limited in num- 

 ber, and are chosen to illustrate the kind of material that is open 

 to us. As in other portions of this series of papers, the subjects 

 treated are to be regarded as representative of a rich field, from 

 which the nature study teacher is privileged to draw. Those 

 here selected are arranged so that they lead to a general progress 

 into larger phenomena and wider generalizations, still within the 

 limit of children of school age. This is not to be regarded as an 

 attempt at teaching the science of physics in the lower grades. 



The following subjects experimentally treated, beside being 

 most excellent material for drill in what nature study is to give, 

 will also furnish a good basis for understanding mnch about heat, 

 air and water, and the large part played by these agencies in the 

 form and structure of the earth's surface. We will begin this 

 series with some simple lessons on heat. 



Heat Expands Water. 



Fill a flask or a bottle with water. Such a flask as given in 

 the figure isrof a kind of glass that can be heated without danger 

 of breaking. Close it with a cork thru which a glass tube passes. 

 A short tube will answer, but if two or thiee feet long it will be 

 better. 



To start with, have sufficient water in the flask to extend up 

 into the tube two or three inches. Be sure to have no air bubbles 

 in with the water. Allow members of the class to fill and arrange 

 the apparatus. Let all see clearly just how everything is arranged. 



