276 



GENESEE FARMER. 



Dec. 



solidifying of water changes insensible into sen- 

 sible heat 1 



3"2. There is. Pour cold water on well burnt 

 caustic lime, and it will disappear, being Svjlidi- 

 iied, and chemically combined with the lime, to 

 form a hydrate of that mineral. In this 0{)era- 

 tion heat enough is often evolved from cold wa- 

 ter to set wood on fire. 



What is the weight of steam, as compared with 

 that of atmospheric air ? 



33. It is 38 per cent, lighter. Air being 1000 

 steam is 620. 



At what temperature does water occupy the 

 smallest space ? 



34. At 39i degrees. It is an important law, 

 ■which so modilies the arrangement among the 

 particles of matter in water, that it expands in 

 the same ratio on being cooled below 39..5°, even 

 after it is frozen into solid ice, that is witnessed 

 when its temperature is raised above 39.5'^' to 

 any number below 212°. Thus water at 32'^ 

 and 47^ fills equal volumes. 



When water at 32° is solidified into ice at the 

 same degree, how much larger space does the 

 ice fill than that occupied by the water ? 



35. About 5 per cent. 100 cubic inches of 

 vater, on freezing, make 10.5 cubic inches of ice. 



Is the expansive force of water, while chrys- 

 talizing, very great ? 



36. It is. This prodigious mechanical force 

 plays a very conspicuous part in dlsintpgraiing 

 solid rocks, and other minerals. 



What are we to understand by the disintegra- 

 tion of any solid substance ? 



37. Take a lump of hard chrystalized sugar, 

 and crush it by any meclianical force, and you 

 ■will disintegrate its particles ; and by so doing, 

 greatly increase the solubility of the sugar. The 

 freezing of a compact lump of clay, separates all 

 its particles, and greatly favors the solution of 

 the salts in this lump of earth, which nature uses 

 in the organization of plants. Heat and Cold 

 are very important agents in the economy of 

 Nature ; and their action on the material ele- 

 ments of the world should be studied with the ut- 

 most care. 



How will you account for the cooling of the 

 air in a room by sprinkling water on the floor in 

 a warm day "? 



38. As the water evaporates, it renders a large 

 amount of the sensible heat in the atmosphere la- 

 tent or insensible, which heat is indispensable to 

 retain water in its expanded condition of vapor. 

 The radiation of heat from the surface of the 

 earth, and from mountains, its interception bv 

 clouds, the capacity of the atmosphere to hold va- 

 por in a gaseous form, and its condensation into 

 dew, rain, and snow, will be fully investigated 

 under the appropriate study of Meteorology. 



Suppose water in lakes and rivers had contin 

 ued to contract in volume when cooled below 

 39i degrees, as it does from 212° down to that 



point J what would be the effect of such a law? 



39. Most disastrous to all land animals and 

 plants in all the regions of the eartli, where win- 

 ter and frost prevail to any extent. Water and 

 ice are good non-conductors of heat ; and by re- 

 taining a covering of ice, and of water below 39^ 

 degrees on the surface of rivers and lakes in win- 

 ter, the escape of heat from the mass of water 

 below is prevented. It is by this means that the 

 fluidity of water is preserved in the coldest 

 weather. 



Suppose Providence had so arranged the par- 

 ticles of ice as to render it 5 per cent, heavier, 

 instead of being 5 per cent, lighter than water, 

 what would be the etlect ? 



40. The ice would sink at once to the bot- 

 tom of the stream or lake as fast as formed ; and 

 the whole body of water would soon become a 

 solid mass of ice, which, in man}' cases, the heat 

 of a whole season could not melt again. 



How will you account for the large cracks in 

 ice on rivers, ponds, and lakes ? 



41. They are made b}- the remarkable influ- 

 ence of heat, which contracts ice, after severe 

 freezing, and opens seams, just as heat in sum- 

 mer opens cracks or fissures in stiff clay. On 

 lake Erie, wide fissures in the ice are often form- 

 ed by its contraction in spring, which being filled 

 with snow evenly over the surface, present to the 

 traveller dangerous and unseen cavities. 



Are the icisdom and goodness of Providence 

 strikingly displayed in the laws that regulate the 

 action of heat and cold on wafer, ice, and vapor ? 



42. They are. The heat of summer would often 

 be insupportable had not God so arranged the el- 

 ements that both vapor and plants absorb and fix 

 a greater or less quantity, according to the inten- 

 sity of the heat. The latent heat in vapor is 

 soon given out to check the too severe cold at 

 night by the radiation of heat from tlie earth's 

 surface ; v,hile the latent heat stored up in the 

 organized carbon and hydrogen of plants, may 

 be kept indefinite ages, for the use of reasoning, 

 accountable Man. Twenty millions of tons of 

 coal are annually taken from the bowels of the 

 earth in Great Britain, every grain of which 

 contains latent heat that was absorbed from an 

 overheated atmosphere tens of thousands, if not 

 millions of years, before man was created on this 

 planet. This latent heat thus long stored up by 

 Providence, now warms millions of our race,, 

 cooks their food, and performs the mechanical 

 labor, through the agency of steam, of a vast, 

 and indefinite number of working men. That 

 mineral coal is of vegefahlc origin, all that have 

 investigated the subject now admit. And that 

 forest trees, and all plants, absorb and fix heat, 

 which is evolved wl:cn they are consumed by 

 fire, or in animals, are facts, the truth of which 

 few will deny, after they have studied with the 

 Author, the Physiology of cultivated plants, and 

 domestic animals. 



