10 BULLETIN 415, U. S. DEPARTMENT OF AGRICULTURE. 



be to make the room, whether in a building or tent, as tight as pos- 

 sible, except for the openings required for ventilation. All chinks 

 should be closed completely. Wherever practicable as hot a fire 

 should be kept up at night as during the day. This is particularly 

 necessary in a tent, where any dying down of the fire at night causes 

 the air to cool rapidly, with consequent delay and loss of time and 

 labor. 



The stove is usually placed in the center of the room and approxi- 

 mately level with the lowest tiers of trays. This results in much 

 slower drying of the cones which are near the bottom of the room 

 and at a distance from the stove. Attempts have been made to obvi- 

 ate this difficulty by dividing the stovepipe into sections and carry- 

 ing it through as much of the room as possible, but without complete 

 success. Better drying is secured in the farther ends of the room, 

 but the bottom remains much cooler than the top. This difference is 

 especially marked in tents, where cold air constantly passes in under 

 the walls. With onfy one stove even distribution of heat is impossi- 

 ble. With stoves set at opposite ends of the tent and connected by a 

 single stovepipe conditions are but little better. In one instance 

 where this arrangement was used a difference of from 20° to 30° F. 

 was found in the temperature of the air at the highest and lowest 

 trays in a six-tier stack. 



One method of hastening the opening of the cones in the lower 

 trays is to raise them as the drying proceeds and the cones in the 

 upper trays are removed. This, however, requires additional han- 

 dling and loss of time. A better method, wherever space is available, 

 is to place the lowest tier of trays somewhat above the stove. Room 

 for air circulation is essential. The tiers of trays should be at least 

 6 inches apart vertically, preferably 8 inches, and the same dis- 

 tance from the walls. 



The best method of securing even distribution of heat, although 

 not always practicable, is to have the drying room heated from 

 below. If conditions permit, an excavation should be made under 

 the building and the stove placed below the floor. This not only 

 heats the room above more evenly, but furnishes additional space 

 for spreading cones. The stovepipes should pass through as many 

 parts of the dry room as possible. Still better results are obtained 

 if hot-air pipes can be conducted from the drum of the stove into 

 the room above, and even more heat can be made available by in- 

 closing the stovepipes in jackets, which need not extend farther 

 than the openings where the pipes pierce the floor. 



Maximum temperatures and duration of heating. — The degree of 

 heat and the length of time required to open cones vary somewhat 

 with different species, but still more with the conditions under 



