146 GENERAL SCIENCE 



stove or furnace, represents a waste of heat liberated in the 

 combustion of the fuel used. While much of this waste is 

 incident to the maintenance of an oxygen supply for keeping 

 up combustion, it is possible to so regulate the dampers of 

 a heating outfit by frequent adjustments as to keep the 

 waste of heat and of its fuel equivalent at a minimum. 

 The heat in the water drawn from reservoir or boiler at a 

 kitchen range may be heat saved rather than lost up the 

 chimney. In the use of gas ranges, too, a careful regulation 

 of the flow of gas will save much unnecessary expense. 

 After water that is being heated has begun boiling it cannot 

 be made any hotter when in an open dish. To keep it boiling 

 thereafter, only enough heat is needed to replace what is 

 being carried off in the escaping vapor. 



SUMMARY 



Temperature means degree of heat. It is entirely independent of 

 the quantity of matter in the body, but is proportional to the rate of 

 motion of the molecules of the body. Heat in a body is the energy it 

 possesses by reason of its molecular motions. 



The measurement of temperature is based upon the principle that 

 changes in volume of a body are proportional to temperature changes. 

 It is assumed that expansion takes place at the same rate as the rise 

 in temperature. As the molecular motion decreases shrinkage in vol- 

 ume and lowering of temperature occur at the same rate. 



The coefficient of expansion is the fraction showing what part of an 

 original length, surface, or volume a body increases per degree rise in 

 temperature. For solids and liquids, it varies with the substance; for 

 all gases, when based upon the gaseous volume at o C., it is ^73 of 

 that volume per degree centigrade, or Y\ per degree Fahrenheit. 



Mercury has many properties adapting it for use in temperature 

 measurements. Enclosed within a sealed glass tube it is readily seen 

 through the glass. Its rise and fall is not interfered with by any adhe- 

 sion to the glass. The wide range in temperature between the freezing 

 and boiling points of mercury covers all ordinary uses of thermometers. 

 Its specific heat, i.e., the amount of heat necessary to change its tern- 



