88 



Introduction to the Study of Science 



other 212 F. There are accordingly ICO steps of the one 

 stairway, and 212 - 32, or 180 steps on the other (Fig. 25). 



To find the equivalent of one scale on the other is simple. 

 On the Centigrade scale 100 steps indicate the same difference 

 in temperature as 180 steps on the Fahrenheit scale. How 

 many steps F. are equivalent to 10 steps C.? How many 

 steps F. to 5 steps C. ? Expressed in the 

 form of a fraction one degree C. is equiva- 

 lent to f of a degree F. What part of 

 one C. degree is one F. degree? 



FAHR. CENT. 

 -.2121 ,-100 



32- -0- 



-18-- 



i B SOLUTE 

 -T-373 " 



FREEZING 

 273 POINT 



Exercise. The reading of a C. scale is 

 50. What is the equivalent on the F. scale? 

 How many steps is this above the freezing 

 point ? 



Find the equivalent on the other scale of 

 each of the following : 14 F. ; 70 C. ; -20 C. ; 

 -40 F.; 37 C. ; 98.4 F. ; 68 F. ; 212 F. ; 

 98 C. ; -273 C. 



39. Kinds of thermometers. Weather 

 B ^ TE Bureau stations of the United States use 

 FIG. 25. Diagram a thermometer known as the " maximum 

 and minimum." The instrument consists 

 of two thermometers, one containing mer- 

 cury for maximum temperatures, and the other alcohol for 

 minimum temperatures. The bore of the maximum or mercury 

 thermometer is very much constricted just above the bulb ; 

 mercury forced by expansion through the constriction cannot 

 return. It registers the maximum temperature during a given 

 period, such as twelve or twenty-four hours. The minimum 

 or alcohol thermometer contains a small index, much like & 

 double-headed pin. The index is drawn downward by the fall 

 of the surface of the alcohol and remains at the lowest point 

 reached until released by the observer. 



The clinical thermometer of medical practice may be men- 

 tioned. It is a maximum mercury thermometer, with Fahren- 



