WINTER EARTH STUDY. 493 



Work and use. How Jack Frost uses ice for his heav- 

 ier, more solid decorations on houses and trees ! How it 

 sparkles in the sunlight, and glistens in the moonlight. 

 How it bridges the brooks and rivers, and covers the lakes 

 and ponds! How it brings to us all the sport of sliding 

 and skating ! How the cold of winter is stored up in the 

 ice (expressed from the children's point of view) and kept 

 in our ice-houses until summer, when it cools our water, 

 and keeps our milk sweet, and helps us take care of our 

 food ! In places where much ice is cut, it may be well to 

 study something of the process of cutting and storing ice. 

 An inspection of an ice-box or refrigator in use, or of a 

 cold-storage room, will impress strongly the usefulness of 

 ice. 



The breaking of pitchers and bursting of water-pipes 

 seem to be pure mischief on the part of Jack Frost. But 

 this is only another illustration of the fact that apparent 

 evils are often great blessings in disguise. This "mis- 

 chief" of Jack Frost, the expanding of ice as it freezes, 

 makes the ice lighter, and causes it to float on the top 

 of the water. If it did not expand, or if it contracted, as 

 most substances do as they change from the liquid to the 

 solid state, our lakes and streams would become solid 

 masses of ice, from bottom to top, which the summer's 

 sun could never melt. This same expansion is the main 

 agent in breaking up our rocks into soil. The water which 

 has soaked into rocks and stones expands as it freezes, 

 making them finer and finer each winter, so that the plant 

 roots can go through them, and get the food they need. 

 Jack Frost is thus one of the best friends of the farmer. 

 The farmer who ploughs in the fall knows that Jack Frost 

 is going to keep on ploughing for him all winter. This 

 work of frost and ice can be best studied in the spring. 

 It is discussed under the topic : " Work of water in soil- 

 uxaking." (See page 513.) 



