584 EVERYDAY SCIENCE 



of cotton wicking in a solution of saltpeter and dry them thoroughly. 

 Of the materials to be found in a forest nothing is better than dried 

 fungus growths of various sorts. Thoroughly dried puff-balls, or 

 the flat white fungus growths found on decaying tree-trunks, or 

 dried lichens or moss are among the best materials. Dust or very 

 fine shavings scraped from dry cedar bark, spruce, or pine will 

 catch the spark readily. 



To obtain the spark, rest the flint on the "punk" and strike 

 downward with the steel along the edge of the flint so as to throw 

 the shower of sparks into the "punk." 



When you have the spark in the "punk," nurse it into a glow 

 exactly as in the case of the rubbing-stick fire, transform the glowing 

 spark into flame with the aid of tinder, and add the kindling and 

 larger fuel gradually until your fire is established. 



PROJECT XIX. How to Operate a Fire-extinguisher, 

 pages 79 and 80 



The principle of the fire-extinguisher which produces carbon 

 dioxide is carefully explained on pages 79 and 80 of the body of 

 the book. Every pupil of junior high school age ought to know 

 how to operate . one of the extinguishers without a moment's 

 hesitation. 



Every modern fire-extinguisher has explicit directions for operat- 

 ing it printed on the metal container. These directions should be 

 followed to the letter. It is especially important that the ex- 

 tinguisher should be discharged occasionally so as to have the 

 machine always charged with fresh chemicals. 



Build a small fire in the open, away from all buildings, and use 

 a fire-extinguisher to smother the fire. Remember that the pur- 

 pose oi these machines is to cover the fire with a blanket of carbon 

 dioxide gas. Play the spray from the machine over the whole fire 

 so as to cut off the oxygen from all burning material. 



When you have extinguished the fire, refill the cylinder according 

 to directions, not neglecting to wash it out thoroughly before re- 

 filling. If you are at all in doubt as to whether you have refilled 



