32 



SCIENTIFIC AMUSEMENTS. 



of freezing water or melting ice. This is effected by marking off 

 the two points on the material to be engraved, so as to form the 

 scale (fig. 15), and then dividing the distance between them into 



I 6 



Boiling point.; oo 



Freezing point 



00 Boiling point 



Freezing point. 



Fig. 17. 



Fig. 16. Fig. 16. 



Fig. 15. Thermometer with attached Scale. 

 Fig. 16. Chemical Thermometer. 



Fig. 17. Diagram showing relationship between the Centigrade, 

 Fahrenheit, and Reaumur scales. 



a number of equal parts, corresponding with the number of degrees 

 between the freezing and boiling points. For the " centigrade " 

 scale of temperature this distance is divided into 100 equal parts, 

 and the graduations are also continued at the same equal intervals 

 above and below the two fixed points ; the ice-point is called 0, 

 and temperatures below this minus so and so (minus ten degrees, 

 minus fifteen degrees, &c., written 10, - 15, and so on) ; the 



