62 Introduction to the Study of Science 



match head. With the burning sulfur several kinds of wood 

 are ignited, for they have a kindling temperature just a little 

 higher than that of sulfur. Thus each of the substances in 

 the match is selected because of its " kindling temperature." 



Does the usual method of laying the materials for a fire in 

 the range or fireplace indicate a knowledge of their different 

 kindling temperatures? Explain how you would arrange the 

 materials for a hard-coal fire in the furnace or range. You may 

 be familiar with what is known as the " hot blast " stove. 

 Is the fuel arranged in the same way in it as in an ordinary 

 stove? Why? Have you tried to make a fire in the woods 

 with only damp wood available? How did you do it? A 

 woodsman does not start a fire with paper. Taking your list 

 of fuels, arrange them in what you think to be the order of the 

 kindling temperature from lowest to highest. Add to your 

 list some substances which are not fuels, as straw, woolen 

 and cotton cloth, iron, asbestos, and so on. From this it will 

 appear that knowledge of the kindling temperatures of different 

 kinds of fuel and other materials is valuable not only in making 

 matches or in starting fire, but in selecting materials for dif- 

 ferent purposes, as clothing and buildings. 



31. Draft in fireplace or stove. As you sit comfortably 

 before the fire in the fireplace or stove, you seldom consider, 

 unless the stove or fireplace smokes, why it draws. When 

 the fire is first lighted, the smoke may issue freely from the 

 stove and fill the room, but after a while it goes up the chimney 

 as desired. Why does it behave in this fashion ? Why, in fact, 

 does it draw at any time? A simple experiment will demon- 

 strate draft very clearly and will aid in understanding its con- 

 ditions. 



Exercise. Provide a box similar to that shown in Fig. 17 with di- 

 mensions about 6" by 6" by 15", with one side covered with a piece of 

 glass and two holes in the top as indicated in the figure. By making 

 a sliding bottom the candle can be shifted from one position to another 

 without opening the box. Over the holes place glass chimneys. 



