180 mature'* 



grees Farhenheit, and at the moment of freez- 

 ing there is a sudden expansion to such an ex- 

 tent that a cubic foot of ice will occupy a 

 much larger space than it will in the form of 

 water; and because it occupies so much larger 

 space it is lighter than the same bulk of water 

 would be, and therefore it floats in water. 



At the point of freezing, the thermometer if 

 placed on the ice will register 32 degrees. If 

 the ice is allowed to melt, the water at the mo- 

 ment of liquefaction would be found to regis- 

 ter the same degree of temperature as the ice 

 when first frozen. And yet there has been a 

 vast expenditure of energy between the points 

 of liquefaction and congelation, notwithstand- 

 ing the temperature of ice may be lowered, 

 after it is formed, many degrees, which is 

 measurable by the thermometer. Suppose we 

 take a piece of ice which is 10 degrees below 

 the freezing point and insert in it a thermom- 

 eter. If now we apply heat to this ice the ther- 

 mometer will gradually rise until it reaches the 

 melting point at 32 degrees Fahrenheit, where 

 it will stand until all the ice is melted. The 

 application of heat is going on steadily, but 

 there are no indications of movement in the 

 mercury until the last trace of ice with which 

 it is in contact has been liquefied. After the 

 ice is all melted, if the application of heat to 

 the body of liquefied ice be continued, the 

 column of mercury will resume its movement 



