order to produce the most satisfactory results,
especially in the drying of hardwoods or heavy softwood timbers,
should be not less than 100 feet in length (see Fig. 35).

In placing this type of kiln in operation, the following instructions
should be carefully followed:

When steam has been turned into the heating coils, and the kiln is
fairly warm, place the first car of material to be dried in the drying
room--preferably in the morning--about 25 feet from the kiln door on
the receiving or loading end of the kiln, blocking the wheels so that
it will remain stationary.

[Illustration: Fig. 35. Exterior View of Four Progressive Dry
Kilns, each 140 Feet long by 18 Feet wide. Cross-wise piling,
fire-proof construction.]

Five hours later, or about noon, run in the second car and stop it
about five feet from the first one placed in the drying room. Five
hours later, or in the evening push car number two up against the
first car; then run in car number three, stopping it about five feet
from car number two.

On the morning of the second day, push car number three against the
others, and then move them all forward about 25 feet, and then run in
car number four, stopping it about five feet from the car in advance
of it. Five hours later, or about noon, run in car number five and
stop it about five feet from car number four. In the evening or about
five hours later, push these cars against the ones ahead, and run in
loaded car number six, stopping it about five feet from the preceding
car.

On the morning of the third day, move all the cars forward about six
feet; then run in loaded car number seven stop it about four feet from
the car preceding it. Five hours later or about noon push this car
against those in advance of it, and run in loaded car number eight
moving all cars forward about six feet, and continue in this manner
until the full complement of cars have been placed in the kiln. When
the kiln has been filled, remove car number one and push all the
remaining cars forward and run in the next loaded car, and continue in
this manner as long as the kiln is in operation.

As the temperature depends principally upon the pressure of steam,
maintain a steam pressure of not less than 80 pounds at all times; it
may range up to as high as 100 pounds. The higher the temperature with
a relatively higher humidity the more rapidly the drying will be
accomplished.

If the above instructions are carried out, th