FARMS—FERMENTATION AND FERMENTS 
through radiators at the bottom and from 
there to the smokestack. A direct pas- 
sage is furnished to be used when the 
fire is being started or when coal is be- 
ing added. Some furnaces are “built to 
sell” by their size and are not furnished 
with a radiator. These will burn more 
fuel and give off less heat. 
The Smoke Pipe 
The smoke pipe should connect to the 
chimney as directly as possible, for elbows 
diminish the draft. The flue should be at 
least 8 inches by 12 inches and should 
have no other opening into it for range 
or fireplace. A clean-out door should be 
provided at the bottom, fitted with a tight 
door, and this door must be kept shut, 
except when cleaning out the flue. 
The Grate 
The grate is one of the most important 
parts of a furnace, and there are many 
kinds to be had. The essential things 
are the removal of the ashes and cin- 
ders from the entire grate surface with- 
out carrying unburned coal with them, 
and the admission of air to secure proper 
combustion of the fuel. In comparing 
furnaces the average diameter of the 
fire pot is taken. The space above must 
be large enough to permit of the thor- 
ough mixing of the gases with air or 
else much heat will be lost by imperfect 
combustion. If soft coal is to be burned 
a larger combustion chamber is needed 
than with hard coal, as the supply of air 
must be greater. 
Furnaces differ in the manner of bring- 
ing the air to be warmed into contact 
with the surfaces heated by the combus- 
tion of the fuel. The area of the heat- 
ing surfaces should be about 60 times 
the area of the grate surface to prevent 
overheating of the air in cold weather. 
Where natural gas is available the 
furnace can be arranged to burn it, but 
it is well to have a coal grate also in 
case the gas should be shut off. Wood 
furnaces are generally more simple in 
construction and are often built to take 
a 4-foot stick. Where wood is cheap 
excellent results may be obtained. The 
smoke should pass through a radiator, 
as in case of coal furnaces. 
933 
Distribution of Hot Air by Means of Pipes 
Much depends upon the location of the 
furnace. It should be placed somewhat 
to the north and west of the center of 
the house—that is, toward the prevailing 
cold winds. As the hot air travels best 
through the pipes leading toward the 
sheltered part of the house and to the 
upper rooms, the pipes leading toward 
the north and west or to the rooms on 
the first floor should be given the prefer- 
ence with respect to length and size. 
Make all pipes as nearly the same length 
as possible and as short as the location 
of the registers will permit. Long hori- 
zontal runs of pipe should be avoided, 
especially in first floor pipes. The pipes 
should pitch upward as sharply as possi- 
ble so the resistance will be less. Hach 
pipe should have a damper near the fur- 
nace. Hach room should have a sepa- 
rate pipe, if possible, or the heat will go 
to the less exposed room when a wind 
is blowing. Exposed pipes should be pro- 
vided with an asbestos covering, even 
when made double; double pipes are the 
best for all work. Bright tin is almost 
always used for hot air pipes, as it rad- 
iates less heat than any other suitable 
material. The registers should be as 
near the furnace as possible. Nothing is 
gained by putting them on the exposed 
side of the room and much heat is lost. 
First floor registers may be placed in the 
floor if wall registers would interfere with 
the pipes to the second floor. Second 
floor registers should be placed in the 
wall so as to avoid the necessity of cut- 
ting carpets and not to furnish recep- 
tacles for dirt. If only the first floor is 
heated the registers should be placed in 
the wall. The net area of the register 
should be about 15 per cent greater than 
the section of its hot air pipe. 
ELMrra I. WILSON, 
T™. S Department of Agriculture. 
Fermentation and Ferments 
No. 1—Insoluble Ferments 
Fermentation is a chemical change pro- 
duced by a class of bodies called fer- 
ments. Insoluble or organized ferments 
are single celled, microscopic plants 
