Transportation on Land 297 



SUGGESTIVE QUESTIONS 



1. Compare advantages and disadvantages of running long trains 

 with heavy locomotives and short trains with medium weight loco- 

 motives. 



2. What practical conditions seem to limit the size of locomotives 

 in length, height, and weight? 



VII. THE PRODUCTION AND CONTROL OF STEAM 



128. Uses of steam. Every one knows something about 

 steam and its behavior in certain conditions. All are familiar 

 with its uses in heating buildings, in cooking, in cleaning, in 

 providing heat for drying such articles as clothes, lumber, 

 fruits, and vegetables, in manufacturing water gas or producer 

 gas (see page 162), and as energy for locomotives and stationary 

 engines. This common knowledge may be taken as the basis 

 for a study of some of the more important facts regarding the 

 nature of steam, its production and control in performing useful 

 work for us. 



129. How steam is generated. We shall begin by study- 

 ing experimentally the principal conditions in which steam is 

 produced. 



Exercise. Into a boiling-flask or beaker put about four ounces of 

 water of freezing temperature if available and cover partly with 

 a piece of asbestos board. Place the vessel over a flame and ob- 

 serve closely the behavior of the water throughout the experiment. 1 



When the water is boiling, hold the thermometer in the vapor just 



1 It will be an aid to careful observation and to the interpretation 

 of the observed facts, if you keep a record of the following points : 



(1) the weight of the water with which you begin the experiment; 



(2) its temperature ; (3) the time required to raise it from its initial 

 temperature to boiling temperature ; (4) the temperature of the water 

 when boiling ; (5) the temperature of the water vapor or steam while 

 it remains in contact with the boiling water ; (6) the effect of addi- 

 tional heat upon boiling water, as its temperature, behavior, and 

 generation of steam ; (7) the behavior of the steam bubbles from the 

 moment and place of their formation to their escape at the surface ; 

 and (8) the difference in their size or volume at different depths and 

 different temperatures of the water. 



