92 Introduction to the Study of Science 



On the Centigrade scale the freezing point is and the boiling 

 point 100. 



One degree Fahrenheit is equivalent to f of one degree Centigrade. 



Maximum and minimum thermometers register the extremes of 

 temperature, generally for a day. 



Physicians use a maximum thermometer called the clinical ther- 

 mometer. 



A hydrogen gas thermometer is the standard for the world. 



A metallic thermometer with a recording apparatus constitutes the 

 thermograph. 



Instruments for measuring temperatures above 650 F. are called 

 pyrometers. 



Alcohol because of its low freezing point is used for temperatures 

 such as occur in the Polar regions. 



Expansion and contraction due to changes in temperature are 

 provided for by builders and engineers. 



Extremely low temperatures have been obtained by the evapora- 

 tion of liquid air, liquid hydrogen, and liquid helium. 



Man has learned how to obtain and use extremes of temperature 

 greater than those found in nature. 



REVIEW QUESTIONS 



1. Mention several important uses of a thermometer. 2. Explain 

 the fact that the mercury in a thermometer rises as the temperature 

 rises. 3. Give some reasons why mercury is more suitable than 

 water for thermometer construction. 4. Why is a large bulb and a 

 small bore desirable? 



5. Give the reading for the freezing point and the boiling point of 

 water on the Fahrenheit and Centigrade scales. 6. Describe the 

 construction and working of a maximum thermometer. Of a mini- 

 mum thermometer. Of a thermograph. What are the advantages 

 of a thermograph? 



7. How can furnace temperatures be estimated? 8. What is the 

 lowest temperature obtained ? How? 



SUGGESTIVE QUESTIONS 



1. If glass expanded more than mercury for the same rise in tem- 

 perature, which way would the mercury in the thermometer move 

 as the temperature rises ? 2. Why are rivets inserted red hot in steel 

 construction? 3. What is the estimated temperature of the sun ex- 

 pressed in degrees Fahrenheit ? 4. Is the center of a steel arch bridge 



