LUMBERING IN PINE REGION OF CALIFORNIA. 85 
yellow pine through a dry kiln on account of the danger from blue 
stain in air drying. A kiln 20 by 100 feet has an average daily 
capacity of 12,000 feet. Thus at a single-band mill the usual kiln 
is about 20 by 75 feet or 20 by 100 feet. Under very unfavorable 
drying conditions such a mill may have a pair of kilns each 20 feet 
wide and 70 feet long. At a double-band mill, operating two shifts, 
the dry-kiln plant consists of two kilns each 20 by 100 feet, if drying 
conditions are favorable. Under less favorable conditions the plant 
is often double that size. 
Dry kilns may be made of masonry, concrete, wood frame, or wood 
crib. Masonry and concrete are said to give the best satisfaction. 
Wood crib is rated as being superior to wood frame construction. 
The cost of the equipment and fittings for a kiln 20 feet wide and 100 
feet long, inside measurement, is about $1,600 f. o. b. factory. With 
a wood crib frame the cost of a kiln of this size in place is from $3,500 
to $4,000. A kiln 20 by 70 feet with wood frame costs about $2,500 
in place. A kiln of the same size costs about $10,000 if the material 
is concrete; and $7,000 if the material is tile. The average cost of 
kiln drying lumber in this region is usually from 75 to 80 cents per 
1,000. The cost of handling is approximately 65 cents per 1,000. 
A portion of the upper grades is usually stored in sheds if it is not 
shipped immediately after air or kiln drying. The construction of 
sufficient shed room to accommodate all upper grades would undoubt- 
edly be an economy, because such sheds, though they involve an 
extra handling, do much to prevent deterioration in the quality of the 
lumber and insure a higher return. Care with wide and thick sugar 
pine lumber pays especially well. All yards in this ^region suffer 
from lumber depreciation by waste or change in grades through 
staining, checking, etc. The amount of this depreciation varies 
with yard conditions and the care in handling. It is generally greater 
in thick lumber than in thin lumber. Yards with unfavorable climatic 
and meteorological conditions suffer more heavily than those with 
good drying conditions. Deterioration takes place in kiln drying and 
surfacing, as well as in air drying. Thus shipping taffies at yards 
differ in amount and quality from mill taffies of lumber. Little is 
now known of the amount of deterioration; but studies are being 
undertaken to determine the amount and extent of depreciation in 
each grade, under different seasoning conditions and methods. 
Sometimes surfaced lumber is shipped from the larger mills in 
order to save on freight charges. Thus, in stumpage appraisals it is 
necessary to add to the sawmill investment enough to cover the cost 
of a planing mill for this purpose, and in computing the cost of 
lumber an allowance must be made for this planing. In most 
instances the planing mill is closely connected with the box factory 
and it is difficult to separate the equipment. For a medium-sized 
