would not suffice to thaw them; and perpetual 
snow and ice, as upon Alpine summits, would 
cover and render uninhabitable those beautiful 
countries in which organic matter flourishes, in 
which vegetation spreads its luxuriant fruitful- 
ness, in which living creatures not only breathe 
and exist, but enjoy the manifold blessings of 
physical comfort which God’s Providence has 
specially created for their benefit. But the Crea- 
tor has beautifully contrived to obviate this. 
Everybody knows that water always freezes at 
that part nearest to the atmosphere, that is to 
say, at the top or upper surface, and not at the 
bottom or under surface. This, however, appears 
to be contradictory to the general laws of heat 
and expansion; and so it is;—for the Maker of 
all things has ordained an especial exception to 
these laws in regard to water, so useful to his 
organic world, so necessary to the comforts, nay, 
the very existence of animal life. In our tem- 
perate latitudes we are not ice-bound; our rivers 
never possess more ice than will thaw in a week 
or ten days under the temperature of spring. 
Water does not contract by the loss of heat, after 
it has reached a certain temperature; on the 
contrary, it expands. Water contracts until it 
reaches 395°, being 74° above the freezing point ; 
it then begins to expand in proportion as its 
temperature descends to that point. The colder 
water consequently rises to the surface. Thus, 
when the liquid has reached 32°, the warmest 
layer of the fluid is at the bottom, the coldest at 
the surface. Here, then, the freezing begins, and 
the ice increases in thickness as the upper ice 
becomes colder. But it never descends to the 
bottom of rivers; otherwise the population of our 
waters, so useful to us as food, and for many 
other purposes, would be wholly destroyed. There 
is another fact: water, in the act of solidifying, 
expands still further; and so powerful is this 
expansion, that it will cleave the hardest and 
most tenacious rocks. No metal can resist its 
power, as may be exemplified by filling the bar- 
rel of a gun with water, sealing it hermetically, 
and placing it in a situation for the water to 
freeze. The expansion will burst the barrel; so 
it would a cannon under similar circumstances. 
See the articles Frrnzine and Frost. 
Under ordinary atmospheric pressure com- 
puted from the level of the sea, pure water boils 
at 212°; though waters containing matters in 
solution, as all our domestic waters do, requirea 
higher temperature to boil. Every 500 feet of 
elevation diminishes the pressure so much, that 
water will boil at one degree less; so that on the 
Peak of Teneriffe, it boils at 192°, and on the 
highest part of the Himalaya range where human 
creatures can breathe, at 170°. In a vacuum, 
water will boil at a much lower temperature than 
this; nay, it will actually boil on the application 
of cold, as the following pretty experiment will 
show. let a clean Florence oil-flask be haif 
filled with water; place it over a lamp until the 
WATER. 
621 
water boils; remove the flask from the fire and 
cork it while still full of steam. The water has 
now ceased to boil; but if the flask be plunged 
into a pail of cold water, the boiling will recom- 
mence. The reason is obvious. The steam 
generated by the boiling alone occupies the space 
in the flask above the water, the atmospheric air 
being expelled by the heat; and the flask being 
corked, the steam remains where it was; but on 
plunging the flask into cold water, the steam is 
condensed by the cold, and falls in the form of | 
water into the liquid beneath it, leaving a vacuum 
above, when the boiling immediately recom- 
mences.— When a vessel containing water is 
placed over a fire, a hissing sound is soon heard 
as the fluid increases in temperature. This is 
caused by the vibrations arising from the vapor- 
isation of the particles of liquid in contact with 
the bottom of the vessel, which being nearest to 
the fire is, of course, the first part heated. These 
particles vaporise and again become condensed 
as they rise, until sufficient heat is imparted to 
the mass of the liquid. As this heats, the sound 
becomes louder, until ebullition begins and steam 
is rapidly evolved. The temperature is now sta- 
tionary ; it never rises above the boiling point, 
nor does the steam formed acquire a higher tem- 
perature. It may be remarked, however, that 
under considerable pressure water may be heated 
to a red heat, that is to say, to a heat which can- 
not exist without light, about 800° Fahrenheit ; 
but the moment the pressure is removed and the 
liquid open to the air, the temperature suddenly 
jumps down to 212°, and steam violently escapes, 
When water is thus heated, the vessel contain- 
ing it becomes red-hot, the water itself being so; 
and this state of things no doubt sometimes 
exists, when not suspected, in steam - engine 
boilers, and in the hot-water apparatus for 
warming churches, dwelling-houses, and manu- 
factories, and may there give rise to very serious 
accidents. See the article Borrine. 
Though steam is generated from water at a 
temperature of 212°, yet this vapour requires a 
thousand degrees more of heat to assume the 
gaseous condition. This fact is shown by the 
following experiment, which we take from Pro- 
| fessor Donovan’s Elements of Chemistry :—“ Ifa 
pound of steam at 212° be received into 5:56 
pounds of water at 32°, the former will be con- 
densed into water; and the whole, amounting to 
6°56 pounds of water, will have the temperature 
of 212°. The temperature of the steam, now 
water, has not been reduced, yet 5°56 pounds of | 
water have been raised from 32° to 212°, that is 
180° for each pound, or 1000° (180° -F 5°56) in 
all. Had a pound of water at 212°, instead of a 
pound of steam at 212°, been mixed with the 
5°56 pounds of water at 32°, the resulting tem- 
perature would only have been 64° instead of 
212°. Hence the number of degrees of heat 
which steam at 212° contains in a latent state, 
and which does not elevate its temperature, is 
