Does 1fce Afloat? 193 



of heat and cold, within certain limits only. 

 If we take water, say, at 50 degrees Fahren- 

 heit and subject it to cold it will gradually 

 contract in bulk until it reaches 39 degrees 

 Fahrenheit. At this point, very curiously, 

 contraction ceases, and here we find the maxi- 

 mum density of water. If the temperature is 

 still lowered we find the bulk is gradually in- 

 creasing instead of diminishing (as is the rule 

 with other fluids), and when it reaches the 

 freezing point there is a sudden and marked 

 expansion, so much so that a cubic foot of ice, 

 which is solidified water, will not weigh as 

 much as a cubic foot of water before it freezes 

 hence it floats. 



Let us try an experiment. Take a small 

 glass flask, terminating in a long neck, say of 

 four to six inches, and of small diameter. 

 Suppose the water in the glass to be at 50 de- 

 grees Fahrenheit. Fill the flask with water 

 until it stands halfway up the neck at 50 de- 

 grees temperature. Now immerse the flask 

 gradually in hot water, and observe the 

 effect. For a moment the water will lower in 

 the neck of che tube, but this is due to the 

 fact that the glass expands before the heat is 

 communicated to the water and enlarges its 

 capacity. But immediately the water will be- 

 gin to rise as the heat is communicated to it, 

 and will continue to expand up to the boiling 

 point. Now take the flask out of the hot 



