AMERICAN AGRICULTURIST. 
[January 
4 
much practical importance, as we shall see. Iron; 
for example, conducts heat freely and rapidly 
through itself ; wood and g'lass feebly and slowly. 
Air conducts very little heat through its substance, 
though it allows radiated heat (in straight lines) to 
pass freely ; and if the air particles are free to 
move, they carry heat from one point to another, 
usually upward, but horizontally when moving 
thus, as in wind currents. 
How Heat is Produced. 
The external, artificial heat used for maintaining 
the warmth of our bodies, beyond what comes from 
the suu, or from air currents, is mainly derived 
from chemical action in burning wood or coal. ! 
One-fifth of air (of its weight) is a gas called oxygen. 
Nine-tenths of water is oxygen. In the air the 
oxygen is simply mixed with another gas (nitrogen) 
and very readily leaves it. In water the oxygen is 
strongly united or combined with another sub¬ 
stance (hydrogen) which it will not readily leave.— 
So, while the free oxygen of the air increases a fire, 
the oxygen is tied up in the water, and water ex¬ 
tinguishes a fire by shutting out free air oxygen. 
Coal, hard or soft, is mainly a substance called 
carbon. Diamonds are pure carbon in a crystal 
form. Almost all substances that grow in plant 
form, and all kinds of flesh, are largely made up of 
this carbon. If we put under cover (to shut out 
air) wood, straw, grain, flour, vegetables, fruits, or 
any kind of flesh, as lean or fat meat, or almost any 
thing used for food, and apply strong heat, we 
drive oil a good deal of water in the form of va¬ 
por, and a little of some other substances, and we 
have a mass of nearly pure carbon or charcoal left 
—in bulk usually as large as the original substance 
heated. This is seen in changing wood into char¬ 
coal under a covering of earth, where a little air is 
admitted at the bottom to burn just enough of the 
wood to heat or char the rest. The same would 
happen to masses of our common food put in place 
of part of the wood. If we admit too much air, 
the charcoal itself will disappear. Charcoal gives 
a hotter fire than wood, because this preliminary 
heating has removed the other substances that in 
turning to vapor and gases absorb and carry off a 
great deal of heat. 
Some Properties of Heat. 
Other preliminary items. Sensible or active heat 
seems to combine with some substances and disap¬ 
pear. If the air in a room should suddenly expand 
to fill two rooms, some heat would disappear, and 
the expanded air would feel much colder. If we 
condense the air suddenly into a much smaller 
space, it will give up heat that was before insensi¬ 
ble. If we put a piece of tinder in the closed end 
of a gun barrel, and with a close-fitting ram-rod 
quickly condense the air upon the tinder, it will 
give out so much heat as to set the tinder on fire. 
If one pint of water be changed to hot or cold va¬ 
por, the vapor will take up and conceal nearly 1,000 
degrees of heat, or heat enough to raise 51 pints of 
water from freezing (32°) to boiling (212°). (If this 
heat was not concealed, or did not disappear, the 
clouds, which are cold water vapor, would be much 
hotter than melted lead.) This heat is similarly con¬ 
cealed, whether the water turns into visible steam 
at 212°, or passes off as cold invisible vapor in the 
air, or in the visible vapor of fogs and clouds. The 
point is, that the evaporation of water, hot or cold, 
invariably produces lower temperature by conceal¬ 
ing and carrying away a great amount of heat. 
We can keep water, milk, etc., cool and render 
them colder, by wrapping the jug, pitcher or other 
containing vessel with cloth and keeping this 
moistened. The evaporation going on carries off 
heat. If the vessel be thin porcelain or earthen 
ware or metal, the heat will pass outwardly to the 
•evaporating surface more readily. Damp or wet 
•clothing, for the same reason, quickly cools the 
body and produces chilliness, and is very likely to 
induce a cold, especially if not uniformly damp, as 
we explained under “ Catching Cold ” last month. 
One point more. When air is warmed, it has the 
power of holding concealed an increased amount 
of water in the form of invisible vapor ; and when 
cooled it gives out this water again in a visible form. 
There is frequently more water in the air above us 
on a hot, clear summer day, than on other dark, 
cloudy, or rainy ones. In the latter case a cold air 
w T ave, or other cause, has reduced the temperature 
of the air above us; it has less capacity for con¬ 
cealed moisture, and gives it up ; the moisture thus 
set at liberty condenses into visible clouds, and if 
the uniting of these little water globules be con¬ 
tinued, they become too heavy to float in the air and 
fall as rain drops. Heating the air in a room makes 
it hide water ; it becomes hungry for more and ex¬ 
tracts it from the skin and from our lungs ; we feel 
parched and disagreeable. Lesson : always keep 
plenty of evaporating water surface in any and ev¬ 
ery room warmed by stove, furnace, or in any way. 
A Fire in the Bloeil. 
When the oxygen of the air unites with the car¬ 
bon of hard coal or charcoal,' or of wood, or of 
flour, meat, or of any other food, a compound is 
formed, viz., a gas, which we call Carbonic Acid. 
The process of forming this compound sets at lib¬ 
erty heat which was before entirely concealed, or 
which existed in another form, and when coal or 
wood is burned rapidly we have a hot fire. The 
same process goes on when wood rots away, but the 
heat is developed so slowly that we do not notice it. 
Precisely the same thing is taking place in the 
human body all the time. The food we eat and digest, 
is in part absorbed into the blood, and carried by it 
everywhere throughout the body. But at the same 
time the blood passing through the lungs is con¬ 
stantly picking up oxygen there from the air which 
we breathe into the lungs, and this, too, goes all 
through the body, aud at millions of points one 
carbon atom of the food is uniting with two 
atoms of oxygen from the air, forming carbonic 
acid, and setting heat at liberty , precisely the same 
as takes place in burning wood or coal in the stove. 
There is only a small product of heat at any one 
point in the blood, but it takes place at so many 
points that there is enough developed to keep up 
the general temperature. And a wonderful provis¬ 
ion it is, that without our supervision, or knowl¬ 
edge even, this ever burning fire goes on within 
us, just so as to keep the whole body at about 98°. 
(We speak only of the main source of animal heat. 
There are other combinations going on in the body, 
which produce more or less heat, such as the union 
of hydrogen from food with oxygen, which escapes 
as water; the union of minute quantities of sulphur 
and of phosphorus with oxygen, etc. Most proba¬ 
bly more or less heat is also derived from the me¬ 
chanical movements of the various organs.) 
If the supply of food fails in the blood for a 
time, from fasting or sickness, then the oxygen in 
the blood attacks any stored up fuel, as fat, flesh and 
other organs of the body, using their carbon to 
keep up the ever necessary warmth. The weight 
of the body grows less, and when no more fat or 
flesh can be found to make heat, cold and death 
come on. The same result follows if the lungs be¬ 
come so diseased as not to furnish the air supply¬ 
ing oxygen fast enough to keep up the internal fire. 
Stop the entrance of air for a few minutes by clos¬ 
ing the windpipe with a cord, or by-filling the lungs 
with water, and heat production stops in the blood, 
the temperature falls below 93' , and the human ma¬ 
chinery ceases to work. 
The carbonic acid produced is poisonous. In the 
stove it escapes through the pipe. That formed in 
the blood is carried to the lungs and thrown out 
into the air. Too many persons breathing in a close 
room fill it with so much carbonic acid that it be¬ 
comes very unhealthful, if not dangerous. 
The blood carries the heat to the surface of the 
body, as well as to all other parts, and a good deal 
of heat escapes off into the air. If the air is cold 
this escape is more rapid, and more heat must be 
produced within to supply the waste. That means 
more fuel, that is more food, or more flesh is con¬ 
sumed.—Remember that the blood must be kept 
up to about 98°. Of course, then, in cold weather 
more food is necessary or the body becomes emaci¬ 
ated. But anything that stops escape of heat from 
the surface of the body, saves food, or saves using 
up flesh. Warm clothing, warm air, warm dwel¬ 
lings, warm stables, warm sheds, all help to stop 
this waste of heat. 
Further Practical Jbessons. 
As to domestic animals, is not the above a pos¬ 
itive proof, that sheltering all animals from cold- 
weather, from chilling winds which by their rapid 
motion carry oil heat more rapidly,is the way to save 
food and to save waste of flesh ? If by stopping this 
waste of heat from the surface all the food con¬ 
sumed will not be wanted to make heat, a portion 
of it can go to increasing the flesh, that is to pro¬ 
ducing growth, or more can be used in making 
milk, eggs, etc., within the animal. 
Dyspeptic persons, those having feeble digestion, 
or a poor appetite, get less internal heat from food 
combustion, and suffer from cold. Such persons 
need a warmer atmosphere, or warmer dwellings, 
and warmer clothing to retain the heat that is pro¬ 
duced. This applies to all animals. 
Close-fitting garments, garters, lacing, boots, 
shoes, neck-ties, etc., that prevent free easy circu¬ 
lation of the blood, each and all diminish the a- 
mount of heat produced, aud its unform distribu¬ 
tion. Exercise promotes more rapid circulation of 
the blood and increased heat production. 
We stated above that evaporation of water car¬ 
ries off much heat. Rubbing wet horses and other 
animals dry is very useful not only to save heat, 
but also to save cold taking, as explained in our 
last number. For the same reason any damp gar¬ 
ments should be replaced with dry ones as soon as 
possible, or enough covering be added to prevent 
chilliness from the evaporation. 
Free perspiration (sweating) in hot weather car¬ 
ries off a large amount of heat, and keeps down 
the temperature. If perspiration be checked, 
sponging with water aids in cases of sun stroke or 
depression from heat. Persons have gone into hot 
ovens unharmed by encasing themselves in moist¬ 
ened garments, the evaporation keeping down the 
heat about the body. Green wood, besides its in¬ 
convenience, is very unprofitable. A large amount 
of heat which the dry portions would yield, is lost 
by being carried off in the evaporation of the sap. 
So of any wet or damp fuel of any kind. 
Confined Ail- a Protection Against Cold. 
As confined air is a poor conductor of heat, all 
fabrics that are porous, that is full of little inter¬ 
stices, tubes, or holes filled with air, are the best 
protectors to keep heat from escaping from the 
surface of the body. A loosely woven garment 
or bed coverlid is warmer than a compact, firmly 
woven one, because the air in the texture of the 
former conducts away heat less rapidly than the 
more solid ones. Loose-fitting garments are warmer 
than close-fitting ones, for reasons above given, 
and also because the air space between them and 
the skin is a non-conductor of heat. 
Stone, brick, or wooden walls with perpendicular 
air spaces in them, are warmer than solid walls, 
because the air couduets heat away less than the 
solid materials. A sheathing of tarred paper, or 
pasteboard, or of any thick paper even, placed mid¬ 
way between the clap-boarding aud the plastering, 
to form two thin air-chambers instead of one, adds 
greatly to the warmth of a house or other building. 
Two half-inch boards, set a little apart to leave an 
air space between, makes a far warmer house wall 
than the same thickness of wood in inch boards. 
A layer of loose straw put between the wall and 
the earth banking up of a cellar, adds much to the 
warmth, on account of the air in the meshes of the 
straw. The same is true in covering roots or apples 
to be left out in heaps over winter. 
Double glass windows are several times warmer 
than single glass, because of the non-conducting 
film of air between. So of double doors. 
Moving air both carries off heat faster of itself, 
and also increases evaporation, thus largely dimin¬ 
ishing the temperature. A very small crack in a 
