NATURE-STUDY LESSONS. 171 



(d) What is the condition of the temperature of the 



water in the lower portion of the tube ? 



(e) What can you infer concerning water as a Heat 



conductor ? 

 5. Compare water with iron or copper in respect to 

 conduction of heat. 



Liquids are generally much poorer conductors than solids. 

 XLIX.-CONVECTION, 



1. (a) Place a test-tube containing water, with a few 



very small particles of coloring matter or 

 scrapings from a piece of rotten, water- 

 soaked wood at its bottom, over the flame 

 of a lamp. Hold the test-tube by a wire. 

 Observe what takes place in the particles 

 at the bottom of the tube as soon as heat 

 is applied. 

 (d) Describe fully this movement. 



2. (a) Compare the temperature of the water at the 



bottom of the tube after heat has been 

 applied a few seconds with the temperature 

 of the water in the upper portion of the 

 tube. 

 (6) Infer what becomes of the water at the bottom 

 when it is heated. 



3. Continue the heating. How does the water at the 

 top of the tube become heated ? 



4. (a) Take a wide-bottomed beaker, place small par- 



ticles of matter in the bottom of the beaker 

 as in the above experiment, and fill with 

 water. Apply the flame of the lamp to the 

 bottom near the edge and observe what 

 takes place. 



