1846.] Water, its Properties and Uses. 63 



40 deg. Falir., when it begins to expand, and continues to do so 

 till it is frozen. We do not stop now to inquire the cause. We 

 would only refer to the practical use of this fact. And this is 

 principally in the renovation and reproduction of soils and the re- 

 ducing of rocks to a fine state preparatory to tlieir being convert- 

 ed into soil. The pores of the earth, baked and packed by the 

 heat of a summer sun, become in autumn replenished with water, 

 which freezes, and by its expansion breaks up the soil, and ren- 

 ders it porous and fine. All the parts are separate from each 

 other, and being finely divided are reduced to a condition for the 

 more ready control of the chemical affinities which are to reduce 

 them to the state of a fertile soil. 



The crevices of rocks are permeated by water, and its smallest 

 openings absorb that fluid, which freezes and cracks them, and 

 breaks down the solid material into small fragments, or even into 

 a fine powder, reducing it at once to almost the condition of a 

 soil. This is the result of the simple mechanical action of water 

 during the process of freezing. Its agency does not end here. No 

 chemical change, w^th very few exceptions, can take place with- 

 out the presence of water. It brings the materials into a fluid 

 state, the state most favorable for the action of chemical aflSnities. 

 It is largely composed of oxygen, a substance whose affinities 

 have an almost infinite range, and by these two attributes it is en- 

 abled to reduce the rocks from which soils are formed into the 

 elements of vegetable food ; but its offices extend still farther. By 

 the growth of vegetables in the soil, these elements are exhaust- 

 ed, and here w^ater again is of use to restore the action which is 

 to renew fertility and restore productiveness. In relation to ma- 

 nures the case is the same. Buried in the soil, and unw^t by this 

 fluid, they might lie for ages unchanged. It is by the decomposi- 

 tion brought about by the agency of water, that they are rendered 

 available as nutriment to growing plants. So that, whether as 

 the medium through which the food is conveyed to the roots of 

 vegetables, or as the origin of those changes which prepare the 

 food, water is an indispensable agent. 



The effects of water in its different states, upon the tempera- 



